diff --git a/src/rpc/abc.cpp b/src/rpc/abc.cpp
index 9b2b7ddcd..01026c0b8 100644
--- a/src/rpc/abc.cpp
+++ b/src/rpc/abc.cpp
@@ -1,96 +1,95 @@
 // Copyright (c) 2017-2020 The Bitcoin developers
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
 #include <config.h>
 #include <consensus/consensus.h>
 #include <rpc/server.h>
 #include <rpc/util.h>
 #include <util/strencodings.h>
 #include <validation.h>
 
 #include <univalue.h>
 
 static UniValue getexcessiveblock(const Config &config,
                                   const JSONRPCRequest &request) {
     if (request.fHelp || request.params.size() != 0) {
         throw std::runtime_error(RPCHelpMan{
             "getexcessiveblock",
             "\nReturn the excessive block size.",
             {},
             RPCResult{"  excessiveBlockSize (integer) block size in bytes\n"},
             RPCExamples{HelpExampleCli("getexcessiveblock", "") +
                         HelpExampleRpc("getexcessiveblock", "")},
         }
                                      .ToString());
     }
 
     UniValue ret(UniValue::VOBJ);
     ret.pushKV("excessiveBlockSize", config.GetMaxBlockSize());
     return ret;
 }
 
 static UniValue setexcessiveblock(Config &config,
                                   const JSONRPCRequest &request) {
     if (request.fHelp || request.params.size() != 1) {
         throw std::runtime_error(RPCHelpMan{
             "setexcessiveblock",
             "\nSet the excessive block size. Excessive blocks will not be used "
             "in the active chain or relayed. This discourages the propagation "
             "of blocks that you consider excessively large.",
             {
-                {"blockSize", RPCArg::Type::NUM, /* opt */ false,
-                 /* default_value */ "",
+                {"blockSize", RPCArg::Type::NUM, RPCArg::Optional::NO,
                  "Excessive block size in bytes.  Must be greater than " +
                      std::to_string(LEGACY_MAX_BLOCK_SIZE) + "."},
             },
             RPCResult{"  blockSize (integer) excessive block size in bytes\n"},
             RPCExamples{HelpExampleCli("setexcessiveblock", "25000000") +
                         HelpExampleRpc("setexcessiveblock", "25000000")},
         }
                                      .ToString());
     }
 
     if (!request.params[0].isNum()) {
         throw JSONRPCError(
             RPC_INVALID_PARAMETER,
             std::string(
                 "Invalid parameter, excessiveblock must be an integer"));
     }
 
     int64_t ebs = request.params[0].get_int64();
 
     // Do not allow maxBlockSize to be set below historic 1MB limit
     if (ebs <= int64_t(LEGACY_MAX_BLOCK_SIZE)) {
         throw JSONRPCError(
             RPC_INVALID_PARAMETER,
             std::string(
                 "Invalid parameter, excessiveblock must be larger than ") +
                 std::to_string(LEGACY_MAX_BLOCK_SIZE));
     }
 
     // Set the new max block size.
     if (!config.SetMaxBlockSize(ebs)) {
         throw JSONRPCError(RPC_INVALID_PARAMETER, "Unexpected error");
     }
 
     // settingsToUserAgentString();
     std::ostringstream ret;
     ret << "Excessive Block set to " << ebs << " bytes.";
     return UniValue(ret.str());
 }
 
 // clang-format off
 static const CRPCCommand commands[] = {
     //  category            name                      actor (function)        argNames
     //  ------------------- ------------------------  ----------------------  ----------
     { "network",            "getexcessiveblock",      getexcessiveblock,      {}},
     { "network",            "setexcessiveblock",      setexcessiveblock,      {"maxBlockSize"}},
 };
 // clang-format on
 
 void RegisterABCRPCCommands(CRPCTable &t) {
     for (unsigned int vcidx = 0; vcidx < ARRAYLEN(commands); vcidx++) {
         t.appendCommand(commands[vcidx].name, &commands[vcidx]);
     }
 }
diff --git a/src/rpc/avalanche.cpp b/src/rpc/avalanche.cpp
index 3488a2823..b574583d5 100644
--- a/src/rpc/avalanche.cpp
+++ b/src/rpc/avalanche.cpp
@@ -1,93 +1,93 @@
 // Copyright (c) 2020 The Bitcoin developers
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
 #include <avalanche.h>
 #include <config.h>
 #include <key_io.h>
 #include <rpc/server.h>
 #include <rpc/util.h>
 #include <util/strencodings.h>
 
 #include <univalue.h>
 
 static UniValue getavalanchekey(const Config &config,
                                 const JSONRPCRequest &request) {
     if (request.fHelp || request.params.size() != 0) {
         throw std::runtime_error(RPCHelpMan{
             "getavalanchekey",
             "\nReturns the key used to sign avalanche messages.\n",
             {},
             RPCResults{},
             RPCExamples{HelpExampleRpc("getavalanchekey", "")},
         }
                                      .ToString());
     }
 
     if (!g_avalanche) {
         throw JSONRPCError(RPC_INTERNAL_ERROR, "Avalanche is not initialized");
     }
 
     return HexStr(g_avalanche->getSessionPubKey());
 }
 
 static UniValue addavalanchepeer(const Config &config,
                                  const JSONRPCRequest &request) {
     if (request.fHelp || request.params.size() != 2) {
         throw std::runtime_error(RPCHelpMan{
             "addavalanchepeer",
             "\nAdd a peer to the set of peer to poll for avalanche.\n",
             {
-                {"nodeid", RPCArg::Type::NUM, /* opt */ false,
-                 /* default_value */ "", "Node to be added to avalanche."},
-                {"publickey", RPCArg::Type::STR_HEX, /* opt */ false,
-                 /* default_value */ "", "The public key of the node."},
+                {"nodeid", RPCArg::Type::NUM, RPCArg::Optional::NO,
+                 "Node to be added to avalanche."},
+                {"publickey", RPCArg::Type::STR_HEX, RPCArg::Optional::NO,
+                 "The public key of the node."},
             },
             RPCResults{},
             RPCExamples{HelpExampleRpc("addavalanchepeer", "5")},
         }
                                      .ToString());
     }
 
     if (!g_avalanche) {
         throw JSONRPCError(RPC_INTERNAL_ERROR, "Avalanche is not initialized");
     }
 
     // Parse nodeid
     if (!request.params[0].isNum()) {
         throw JSONRPCError(
             RPC_INVALID_PARAMETER,
             std::string("Invalid parameter, nodeid must be an integer"));
     }
 
     NodeId nodeid = request.params[0].get_int64();
 
     // Parse the pubkey
     const std::string keyHex = request.params[1].get_str();
     if ((keyHex.length() != 2 * CPubKey::COMPRESSED_PUBLIC_KEY_SIZE &&
          keyHex.length() != 2 * CPubKey::PUBLIC_KEY_SIZE) ||
         !IsHex(keyHex)) {
         throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY,
                            strprintf("Invalid public key: %s\n", keyHex));
     }
 
     CPubKey pubkey{HexToPubKey(keyHex)};
 
     g_avalanche->addPeer(nodeid, 0, pubkey);
     return {};
 }
 
 // clang-format off
 static const CRPCCommand commands[] = {
     //  category            name                      actor (function)        argNames
     //  ------------------- ------------------------  ----------------------  ----------
     { "avalanche",          "getavalanchekey",        getavalanchekey,        {}},
     { "avalanche",          "addavalanchepeer",       addavalanchepeer,       {"nodeid"}},
 };
 // clang-format on
 
 void RegisterAvalancheRPCCommands(CRPCTable &t) {
     for (unsigned int vcidx = 0; vcidx < ARRAYLEN(commands); vcidx++) {
         t.appendCommand(commands[vcidx].name, &commands[vcidx]);
     }
 }
diff --git a/src/rpc/blockchain.cpp b/src/rpc/blockchain.cpp
index 186c26d04..f05157c39 100644
--- a/src/rpc/blockchain.cpp
+++ b/src/rpc/blockchain.cpp
@@ -1,2756 +1,2731 @@
 // Copyright (c) 2010 Satoshi Nakamoto
 // Copyright (c) 2009-2016 The Bitcoin Core developers
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
 #include <rpc/blockchain.h>
 
 #include <amount.h>
 #include <chain.h>
 #include <chainparams.h>
 #include <checkpoints.h>
 #include <coins.h>
 #include <config.h>
 #include <consensus/validation.h>
 #include <core_io.h>
 #include <hash.h>
 #include <index/txindex.h>
 #include <key_io.h>
 #include <node/coinstats.h>
 #include <policy/policy.h>
 #include <primitives/transaction.h>
 #include <rpc/server.h>
 #include <rpc/util.h>
 #include <script/descriptor.h>
 #include <streams.h>
 #include <sync.h>
 #include <txdb.h>
 #include <txmempool.h>
 #include <util/strencodings.h>
 #include <util/system.h>
 #include <util/validation.h>
 #include <validation.h>
 #include <validationinterface.h>
 #include <versionbitsinfo.h> // For VersionBitsDeploymentInfo
 #include <warnings.h>
 
 #include <boost/thread/thread.hpp> // boost::thread::interrupt
 
 #include <condition_variable>
 #include <cstdint>
 #include <memory>
 #include <mutex>
 
 struct CUpdatedBlock {
     uint256 hash;
     int height;
 };
 
 static Mutex cs_blockchange;
 static std::condition_variable cond_blockchange;
 static CUpdatedBlock latestblock;
 
 /**
  * Calculate the difficulty for a given block index.
  */
 double GetDifficulty(const CBlockIndex *blockindex) {
     assert(blockindex);
 
     int nShift = (blockindex->nBits >> 24) & 0xff;
     double dDiff = double(0x0000ffff) / double(blockindex->nBits & 0x00ffffff);
 
     while (nShift < 29) {
         dDiff *= 256.0;
         nShift++;
     }
     while (nShift > 29) {
         dDiff /= 256.0;
         nShift--;
     }
 
     return dDiff;
 }
 
 static int ComputeNextBlockAndDepth(const CBlockIndex *tip,
                                     const CBlockIndex *blockindex,
                                     const CBlockIndex *&next) {
     next = tip->GetAncestor(blockindex->nHeight + 1);
     if (next && next->pprev == blockindex) {
         return tip->nHeight - blockindex->nHeight + 1;
     }
     next = nullptr;
     return blockindex == tip ? 1 : -1;
 }
 
 UniValue blockheaderToJSON(const CBlockIndex *tip,
                            const CBlockIndex *blockindex) {
     UniValue result(UniValue::VOBJ);
     result.pushKV("hash", blockindex->GetBlockHash().GetHex());
     const CBlockIndex *pnext;
     int confirmations = ComputeNextBlockAndDepth(tip, blockindex, pnext);
     result.pushKV("confirmations", confirmations);
     result.pushKV("height", blockindex->nHeight);
     result.pushKV("version", blockindex->nVersion);
     result.pushKV("versionHex", strprintf("%08x", blockindex->nVersion));
     result.pushKV("merkleroot", blockindex->hashMerkleRoot.GetHex());
     result.pushKV("time", int64_t(blockindex->nTime));
     result.pushKV("mediantime", int64_t(blockindex->GetMedianTimePast()));
     result.pushKV("nonce", uint64_t(blockindex->nNonce));
     result.pushKV("bits", strprintf("%08x", blockindex->nBits));
     result.pushKV("difficulty", GetDifficulty(blockindex));
     result.pushKV("chainwork", blockindex->nChainWork.GetHex());
     result.pushKV("nTx", uint64_t(blockindex->nTx));
 
     if (blockindex->pprev) {
         result.pushKV("previousblockhash",
                       blockindex->pprev->GetBlockHash().GetHex());
     }
     if (pnext) {
         result.pushKV("nextblockhash", pnext->GetBlockHash().GetHex());
     }
     return result;
 }
 
 UniValue blockToJSON(const CBlock &block, const CBlockIndex *tip,
                      const CBlockIndex *blockindex, bool txDetails) {
     UniValue result(UniValue::VOBJ);
     result.pushKV("hash", blockindex->GetBlockHash().GetHex());
     const CBlockIndex *pnext;
     int confirmations = ComputeNextBlockAndDepth(tip, blockindex, pnext);
     result.pushKV("confirmations", confirmations);
     result.pushKV("size", (int)::GetSerializeSize(block, PROTOCOL_VERSION));
     result.pushKV("height", blockindex->nHeight);
     result.pushKV("version", block.nVersion);
     result.pushKV("versionHex", strprintf("%08x", block.nVersion));
     result.pushKV("merkleroot", block.hashMerkleRoot.GetHex());
     UniValue txs(UniValue::VARR);
     for (const auto &tx : block.vtx) {
         if (txDetails) {
             UniValue objTx(UniValue::VOBJ);
             TxToUniv(*tx, uint256(), objTx, true, RPCSerializationFlags());
             txs.push_back(objTx);
         } else {
             txs.push_back(tx->GetId().GetHex());
         }
     }
     result.pushKV("tx", txs);
     result.pushKV("time", block.GetBlockTime());
     result.pushKV("mediantime", int64_t(blockindex->GetMedianTimePast()));
     result.pushKV("nonce", uint64_t(block.nNonce));
     result.pushKV("bits", strprintf("%08x", block.nBits));
     result.pushKV("difficulty", GetDifficulty(blockindex));
     result.pushKV("chainwork", blockindex->nChainWork.GetHex());
     result.pushKV("nTx", uint64_t(blockindex->nTx));
 
     if (blockindex->pprev) {
         result.pushKV("previousblockhash",
                       blockindex->pprev->GetBlockHash().GetHex());
     }
     if (pnext) {
         result.pushKV("nextblockhash", pnext->GetBlockHash().GetHex());
     }
     return result;
 }
 
 static UniValue getblockcount(const Config &config,
                               const JSONRPCRequest &request) {
     if (request.fHelp || request.params.size() != 0) {
         throw std::runtime_error(RPCHelpMan{
             "getblockcount",
             "\nReturns the number of blocks in the longest blockchain.\n",
             {},
             RPCResult{"n    (numeric) The current block count\n"},
             RPCExamples{HelpExampleCli("getblockcount", "") +
                         HelpExampleRpc("getblockcount", "")},
         }
                                      .ToString());
     }
 
     LOCK(cs_main);
     return ::ChainActive().Height();
 }
 
 static UniValue getbestblockhash(const Config &config,
                                  const JSONRPCRequest &request) {
     if (request.fHelp || request.params.size() != 0) {
         throw std::runtime_error(RPCHelpMan{
             "getbestblockhash",
             "\nReturns the hash of the best (tip) block in the "
             "longest blockchain.\n",
             {},
             RPCResult{"\"hex\"      (string) the block hash, hex-encoded\n"},
             RPCExamples{HelpExampleCli("getbestblockhash", "") +
                         HelpExampleRpc("getbestblockhash", "")},
         }
                                      .ToString());
     }
 
     LOCK(cs_main);
     return ::ChainActive().Tip()->GetBlockHash().GetHex();
 }
 
 UniValue getfinalizedblockhash(const Config &config,
                                const JSONRPCRequest &request) {
     if (request.fHelp || request.params.size() != 0) {
         throw std::runtime_error(RPCHelpMan{
             "getfinalizedblockhash",
             "\nReturns the hash of the currently finalized block\n",
             {},
             RPCResult{"\"hex\"      (string) the block hash hex-encoded\n"},
             RPCExamples{HelpExampleCli("getfinalizedblockhash", "") +
                         HelpExampleRpc("getfinalizedblockhash", "")},
         }
                                      .ToString());
     }
 
     LOCK(cs_main);
     const CBlockIndex *blockIndexFinalized = GetFinalizedBlock();
     if (blockIndexFinalized) {
         return blockIndexFinalized->GetBlockHash().GetHex();
     }
     return UniValue(UniValue::VSTR);
 }
 
 void RPCNotifyBlockChange(bool ibd, const CBlockIndex *pindex) {
     if (pindex) {
         std::lock_guard<std::mutex> lock(cs_blockchange);
         latestblock.hash = pindex->GetBlockHash();
         latestblock.height = pindex->nHeight;
     }
     cond_blockchange.notify_all();
 }
 
 static UniValue waitfornewblock(const Config &config,
                                 const JSONRPCRequest &request) {
     if (request.fHelp || request.params.size() > 1) {
         throw std::runtime_error(RPCHelpMan{
             "waitfornewblock",
             "\nWaits for a specific new block and returns useful "
             "info about it.\n"
             "\nReturns the current block on timeout or exit.\n",
             {
-                {"timeout", RPCArg::Type::NUM, /* opt */ true,
-                 /* default_val */ "0",
+                {"timeout", RPCArg::Type::NUM, /* default */ "0",
                  "Time in milliseconds to wait for a response. 0 indicates no "
                  "timeout."},
             },
             RPCResult{"{                           (json object)\n"
                       "  \"hash\" : {       (string) The blockhash\n"
                       "  \"height\" : {     (int) Block height\n"
                       "}\n"},
             RPCExamples{HelpExampleCli("waitfornewblock", "1000") +
                         HelpExampleRpc("waitfornewblock", "1000")},
         }
                                      .ToString());
     }
     int timeout = 0;
     if (!request.params[0].isNull()) {
         timeout = request.params[0].get_int();
     }
 
     CUpdatedBlock block;
     {
         WAIT_LOCK(cs_blockchange, lock);
         block = latestblock;
         if (timeout) {
             cond_blockchange.wait_for(
                 lock, std::chrono::milliseconds(timeout), [&block] {
                     return latestblock.height != block.height ||
                            latestblock.hash != block.hash || !IsRPCRunning();
                 });
         } else {
             cond_blockchange.wait(lock, [&block] {
                 return latestblock.height != block.height ||
                        latestblock.hash != block.hash || !IsRPCRunning();
             });
         }
         block = latestblock;
     }
     UniValue ret(UniValue::VOBJ);
     ret.pushKV("hash", block.hash.GetHex());
     ret.pushKV("height", block.height);
     return ret;
 }
 
 static UniValue waitforblock(const Config &config,
                              const JSONRPCRequest &request) {
     if (request.fHelp || request.params.size() < 1 ||
         request.params.size() > 2) {
         throw std::runtime_error(RPCHelpMan{
             "waitforblock",
             "\nWaits for a specific new block and returns useful "
             "info about it.\n"
             "\nReturns the current block on timeout or exit.\n",
             {
-                {"blockhash", RPCArg::Type::STR_HEX, /* opt */ false,
-                 /* default_val */ "", "Block hash to wait for."},
-                {"timeout", RPCArg::Type::NUM, /* opt */ true,
-                 /* default_val */ "0",
+                {"blockhash", RPCArg::Type::STR_HEX, RPCArg::Optional::NO,
+                 "Block hash to wait for."},
+                {"timeout", RPCArg::Type::NUM, /* default */ "0",
                  "Time in milliseconds to wait for a response. 0 "
                  "indicates no timeout."},
             },
             RPCResult{"{                           (json object)\n"
                       "  \"hash\" : {       (string) The blockhash\n"
                       "  \"height\" : {     (int) Block height\n"
                       "}\n"},
             RPCExamples{HelpExampleCli("waitforblock",
                                        "\"0000000000079f8ef3d2c688c244eb7a4"
                                        "570b24c9ed7b4a8c619eb02596f8862\", "
                                        "1000") +
                         HelpExampleRpc("waitforblock",
                                        "\"0000000000079f8ef3d2c688c244eb7a4"
                                        "570b24c9ed7b4a8c619eb02596f8862\", "
                                        "1000")},
         }
                                      .ToString());
     }
 
     int timeout = 0;
 
     BlockHash hash(ParseHashV(request.params[0], "blockhash"));
 
     if (!request.params[1].isNull()) {
         timeout = request.params[1].get_int();
     }
 
     CUpdatedBlock block;
     {
         WAIT_LOCK(cs_blockchange, lock);
         if (timeout) {
             cond_blockchange.wait_for(
                 lock, std::chrono::milliseconds(timeout), [&hash] {
                     return latestblock.hash == hash || !IsRPCRunning();
                 });
         } else {
             cond_blockchange.wait(lock, [&hash] {
                 return latestblock.hash == hash || !IsRPCRunning();
             });
         }
         block = latestblock;
     }
 
     UniValue ret(UniValue::VOBJ);
     ret.pushKV("hash", block.hash.GetHex());
     ret.pushKV("height", block.height);
     return ret;
 }
 
 static UniValue waitforblockheight(const Config &config,
                                    const JSONRPCRequest &request) {
     if (request.fHelp || request.params.size() < 1 ||
         request.params.size() > 2) {
         throw std::runtime_error(RPCHelpMan{
             "waitforblockheight",
             "\nWaits for (at least) block height and returns the "
             "height and hash\nof the current tip.\n"
             "\nReturns the current block on timeout or exit.\n",
             {
-                {"height", RPCArg::Type::NUM, /* opt */ false,
-                 /* default_val */ "", "Block height to wait for."},
-                {"timeout", RPCArg::Type::NUM, /* opt */ true,
-                 /* default_val */ "0",
+                {"height", RPCArg::Type::NUM, RPCArg::Optional::NO,
+                 "Block height to wait for."},
+                {"timeout", RPCArg::Type::NUM, /* default */ "0",
                  "Time in milliseconds to wait for a response. 0 "
                  "indicates no timeout."},
             },
             RPCResult{"{                           (json object)\n"
                       "  \"hash\" : {       (string) The blockhash\n"
                       "  \"height\" : {     (int) Block height\n"
                       "}\n"},
             RPCExamples{HelpExampleCli("waitforblockheight", "\"100\", 1000") +
                         HelpExampleRpc("waitforblockheight", "\"100\", 1000")},
         }
                                      .ToString());
     }
 
     int timeout = 0;
 
     int height = request.params[0].get_int();
 
     if (!request.params[1].isNull()) {
         timeout = request.params[1].get_int();
     }
 
     CUpdatedBlock block;
     {
         WAIT_LOCK(cs_blockchange, lock);
         if (timeout) {
             cond_blockchange.wait_for(
                 lock, std::chrono::milliseconds(timeout), [&height] {
                     return latestblock.height >= height || !IsRPCRunning();
                 });
         } else {
             cond_blockchange.wait(lock, [&height] {
                 return latestblock.height >= height || !IsRPCRunning();
             });
         }
         block = latestblock;
     }
     UniValue ret(UniValue::VOBJ);
     ret.pushKV("hash", block.hash.GetHex());
     ret.pushKV("height", block.height);
     return ret;
 }
 
 static UniValue
 syncwithvalidationinterfacequeue(const Config &config,
                                  const JSONRPCRequest &request) {
     if (request.fHelp || request.params.size() > 0) {
         throw std::runtime_error(RPCHelpMan{
             "syncwithvalidationinterfacequeue",
             "\nWaits for the validation interface queue to catch up on "
             "everything that was there when we entered this function.\n",
             {},
             RPCResults{},
             RPCExamples{HelpExampleCli("syncwithvalidationinterfacequeue", "") +
                         HelpExampleRpc("syncwithvalidationinterfacequeue", "")},
         }
                                      .ToString());
     }
     SyncWithValidationInterfaceQueue();
     return NullUniValue;
 }
 
 static UniValue getdifficulty(const Config &config,
                               const JSONRPCRequest &request) {
     if (request.fHelp || request.params.size() != 0) {
         throw std::runtime_error(RPCHelpMan{
             "getdifficulty",
             "\nReturns the proof-of-work difficulty as a multiple of the "
             "minimum difficulty.\n",
             {},
             RPCResult{"n.nnn       (numeric) the proof-of-work difficulty as a "
                       "multiple of the minimum difficulty.\n"},
             RPCExamples{HelpExampleCli("getdifficulty", "") +
                         HelpExampleRpc("getdifficulty", "")},
         }
                                      .ToString());
     }
 
     LOCK(cs_main);
     return GetDifficulty(::ChainActive().Tip());
 }
 
 static std::string EntryDescriptionString() {
     return "    \"size\" : n,             (numeric) transaction size.\n"
            "    \"fee\" : n,              (numeric) transaction fee in " +
            CURRENCY_UNIT + "(DEPRECATED)" +
            "\n"
            "    \"modifiedfee\" : n,      (numeric) transaction fee with fee "
            "deltas used for mining priority (DEPRECATED)\n"
            "    \"time\" : n,             (numeric) local time transaction "
            "entered pool in seconds since 1 Jan 1970 GMT\n"
            "    \"height\" : n,           (numeric) block height when "
            "transaction entered pool\n"
            "    \"descendantcount\" : n,  (numeric) number of in-mempool "
            "descendant transactions (including this one)\n"
            "    \"descendantsize\" : n,   (numeric) transaction size "
            "of in-mempool descendants (including this one)\n"
            "    \"descendantfees\" : n,   (numeric) modified fees (see above) "
            "of in-mempool descendants (including this one) (DEPRECATED)\n"
            "    \"ancestorcount\" : n,    (numeric) number of in-mempool "
            "ancestor transactions (including this one)\n"
            "    \"ancestorsize\" : n,     (numeric) transaction size "
            "of in-mempool ancestors (including this one)\n"
            "    \"ancestorfees\" : n,     (numeric) modified fees (see above) "
            "of in-mempool ancestors (including this one) (DEPRECATED)\n"
            "    \"fees\" : {\n"
            "        \"base\" : n,         (numeric) transaction fee in " +
            CURRENCY_UNIT +
            "\n"
            "        \"modified\" : n,     (numeric) transaction fee with fee "
            "deltas used for mining priority in " +
            CURRENCY_UNIT +
            "\n"
            "        \"ancestor\" : n,     (numeric) modified fees (see above) "
            "of in-mempool ancestors (including this one) in " +
            CURRENCY_UNIT +
            "\n"
            "        \"descendant\" : n,   (numeric) modified fees (see above) "
            "of in-mempool descendants (including this one) in " +
            CURRENCY_UNIT +
            "\n"
            "    }\n"
            "    \"depends\" : [           (array) unconfirmed transactions "
            "used as inputs for this transaction\n"
            "        \"transactionid\",    (string) parent transaction id\n"
            "       ... ]\n"
            "    \"spentby\" : [           (array) unconfirmed transactions "
            "spending outputs from this transaction\n"
            "        \"transactionid\",    (string) child transaction id\n"
            "       ... ]\n";
 }
 
 static void entryToJSON(const CTxMemPool &pool, UniValue &info,
                         const CTxMemPoolEntry &e)
     EXCLUSIVE_LOCKS_REQUIRED(pool.cs) {
     AssertLockHeld(pool.cs);
 
     UniValue fees(UniValue::VOBJ);
     fees.pushKV("base", ValueFromAmount(e.GetFee()));
     fees.pushKV("modified", ValueFromAmount(e.GetModifiedFee()));
     fees.pushKV("ancestor", ValueFromAmount(e.GetModFeesWithAncestors()));
     fees.pushKV("descendant", ValueFromAmount(e.GetModFeesWithDescendants()));
     info.pushKV("fees", fees);
 
     info.pushKV("size", (int)e.GetTxSize());
     info.pushKV("fee", ValueFromAmount(e.GetFee()));
     info.pushKV("modifiedfee", ValueFromAmount(e.GetModifiedFee()));
     info.pushKV("time", e.GetTime());
     info.pushKV("height", (int)e.GetHeight());
     info.pushKV("descendantcount", e.GetCountWithDescendants());
     info.pushKV("descendantsize", e.GetSizeWithDescendants());
     info.pushKV("descendantfees", e.GetModFeesWithDescendants() / SATOSHI);
     info.pushKV("ancestorcount", e.GetCountWithAncestors());
     info.pushKV("ancestorsize", e.GetSizeWithAncestors());
     info.pushKV("ancestorfees", e.GetModFeesWithAncestors() / SATOSHI);
     const CTransaction &tx = e.GetTx();
     std::set<std::string> setDepends;
     for (const CTxIn &txin : tx.vin) {
         if (pool.exists(txin.prevout.GetTxId())) {
             setDepends.insert(txin.prevout.GetTxId().ToString());
         }
     }
 
     UniValue depends(UniValue::VARR);
     for (const std::string &dep : setDepends) {
         depends.push_back(dep);
     }
 
     info.pushKV("depends", depends);
 
     UniValue spent(UniValue::VARR);
     const CTxMemPool::txiter &it = pool.mapTx.find(tx.GetId());
     const CTxMemPool::setEntries &setChildren = pool.GetMemPoolChildren(it);
     for (CTxMemPool::txiter childiter : setChildren) {
         spent.push_back(childiter->GetTx().GetId().ToString());
     }
 
     info.pushKV("spentby", spent);
 }
 
 UniValue MempoolToJSON(const CTxMemPool &pool, bool verbose) {
     if (verbose) {
         LOCK(pool.cs);
         UniValue o(UniValue::VOBJ);
         for (const CTxMemPoolEntry &e : pool.mapTx) {
             const uint256 &txid = e.GetTx().GetId();
             UniValue info(UniValue::VOBJ);
             entryToJSON(pool, info, e);
             // Mempool has unique entries so there is no advantage in using
             // UniValue::pushKV, which checks if the key already exists in O(N).
             // UniValue::__pushKV is used instead which currently is O(1).
             o.__pushKV(txid.ToString(), info);
         }
         return o;
     } else {
         std::vector<uint256> vtxids;
         pool.queryHashes(vtxids);
 
         UniValue a(UniValue::VARR);
         for (const uint256 &txid : vtxids) {
             a.push_back(txid.ToString());
         }
 
         return a;
     }
 }
 
 static UniValue getrawmempool(const Config &config,
                               const JSONRPCRequest &request) {
     if (request.fHelp || request.params.size() > 1) {
         throw std::runtime_error(RPCHelpMan{
             "getrawmempool",
             "\nReturns all transaction ids in memory pool as a json "
             "array of string transaction ids.\n"
             "\nHint: use getmempoolentry to fetch a specific "
             "transaction from the mempool.\n",
             {
-                {"verbose", RPCArg::Type::BOOL, /* opt */ true,
-                 /* default_val */ "false",
+                {"verbose", RPCArg::Type::BOOL, /* default */ "false",
                  "True for a json object, false for array of "
                  "transaction ids"},
             },
             RPCResult{"for verbose = false",
                       "[                     (json array of string)\n"
                       "  \"transactionid\"     (string) The transaction id\n"
                       "  ,...\n"
                       "]\n"
                       "\nResult: (for verbose = true):\n"
                       "{                           (json object)\n"
                       "  \"transactionid\" : {       (json object)\n" +
                           EntryDescriptionString() +
                           "  }, ...\n"
                           "}\n"},
             RPCExamples{HelpExampleCli("getrawmempool", "true") +
                         HelpExampleRpc("getrawmempool", "true")},
         }
                                      .ToString());
     }
 
     bool fVerbose = false;
     if (!request.params[0].isNull()) {
         fVerbose = request.params[0].get_bool();
     }
 
     return MempoolToJSON(::g_mempool, fVerbose);
 }
 
 static UniValue getmempoolancestors(const Config &config,
                                     const JSONRPCRequest &request) {
     if (request.fHelp || request.params.size() < 1 ||
         request.params.size() > 2) {
         throw std::runtime_error(RPCHelpMan{
             "getmempoolancestors",
             "\nIf txid is in the mempool, returns all in-mempool "
             "ancestors.\n",
             {
-                {"txid", RPCArg::Type::STR_HEX, /* opt */ false,
-                 /* default_val */ "",
+                {"txid", RPCArg::Type::STR_HEX, RPCArg::Optional::NO,
                  "The transaction id (must be in mempool)"},
-                {"verbose", RPCArg::Type::BOOL, /* opt */ true,
-                 /* default_val */ "false",
+                {"verbose", RPCArg::Type::BOOL, /* default */ "false",
                  "True for a json object, false for array of "
                  "transaction ids"},
             },
             {
                 RPCResult{
                     "for verbose = false",
                     "[                       (json array of strings)\n"
                     "  \"transactionid\"           (string) The transaction id "
                     "of an in-mempool ancestor transaction\n"
                     "  ,...\n"
                     "]\n"},
                 RPCResult{"for verbose = true",
                           "{                           (json object)\n"
                           "  \"transactionid\" : {       (json object)\n" +
                               EntryDescriptionString() +
                               "  }, ...\n"
                               "}\n"},
             },
             RPCExamples{HelpExampleCli("getmempoolancestors", "\"mytxid\"") +
                         HelpExampleRpc("getmempoolancestors", "\"mytxid\"")},
         }
                                      .ToString());
     }
 
     bool fVerbose = false;
     if (!request.params[1].isNull()) {
         fVerbose = request.params[1].get_bool();
     }
 
     TxId txid(ParseHashV(request.params[0], "parameter 1"));
 
     LOCK(g_mempool.cs);
 
     CTxMemPool::txiter it = g_mempool.mapTx.find(txid);
     if (it == g_mempool.mapTx.end()) {
         throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY,
                            "Transaction not in mempool");
     }
 
     CTxMemPool::setEntries setAncestors;
     uint64_t noLimit = std::numeric_limits<uint64_t>::max();
     std::string dummy;
     g_mempool.CalculateMemPoolAncestors(*it, setAncestors, noLimit, noLimit,
                                         noLimit, noLimit, dummy, false);
 
     if (!fVerbose) {
         UniValue o(UniValue::VARR);
         for (CTxMemPool::txiter ancestorIt : setAncestors) {
             o.push_back(ancestorIt->GetTx().GetId().ToString());
         }
 
         return o;
     } else {
         UniValue o(UniValue::VOBJ);
         for (CTxMemPool::txiter ancestorIt : setAncestors) {
             const CTxMemPoolEntry &e = *ancestorIt;
             const TxId &_txid = e.GetTx().GetId();
             UniValue info(UniValue::VOBJ);
             entryToJSON(::g_mempool, info, e);
             o.pushKV(_txid.ToString(), info);
         }
         return o;
     }
 }
 
 static UniValue getmempooldescendants(const Config &config,
                                       const JSONRPCRequest &request) {
     if (request.fHelp || request.params.size() < 1 ||
         request.params.size() > 2) {
         throw std::runtime_error(RPCHelpMan{
             "getmempooldescendants",
             "\nIf txid is in the mempool, returns all in-mempool "
             "descendants.\n",
             {
-                {"txid", RPCArg::Type::STR_HEX, /* opt */ false,
-                 /* default_val */ "",
+                {"txid", RPCArg::Type::STR_HEX, RPCArg::Optional::NO,
                  "The transaction id (must be in mempool)"},
-                {"verbose", RPCArg::Type::BOOL, /* opt */ true,
-                 /* default_val */ "false",
+                {"verbose", RPCArg::Type::BOOL, /* default */ "false",
                  "True for a json object, false for array of "
                  "transaction ids"},
             },
             {
                 RPCResult{
                     "for verbose = false",
                     "[                       (json array of strings)\n"
                     "  \"transactionid\"           (string) The transaction id "
                     "of an in-mempool descendant transaction\n"
                     "  ,...\n"
                     "]\n"},
                 RPCResult{"for verbose = true",
                           "{                           (json object)\n"
                           "  \"transactionid\" : {       (json object)\n" +
                               EntryDescriptionString() +
                               "  }, ...\n"
                               "}\n"},
             },
             RPCExamples{HelpExampleCli("getmempooldescendants", "\"mytxid\"") +
                         HelpExampleRpc("getmempooldescendants", "\"mytxid\"")},
         }
                                      .ToString());
     }
 
     bool fVerbose = false;
     if (!request.params[1].isNull()) {
         fVerbose = request.params[1].get_bool();
     }
 
     TxId txid(ParseHashV(request.params[0], "parameter 1"));
 
     LOCK(g_mempool.cs);
 
     CTxMemPool::txiter it = g_mempool.mapTx.find(txid);
     if (it == g_mempool.mapTx.end()) {
         throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY,
                            "Transaction not in mempool");
     }
 
     CTxMemPool::setEntries setDescendants;
     g_mempool.CalculateDescendants(it, setDescendants);
     // CTxMemPool::CalculateDescendants will include the given tx
     setDescendants.erase(it);
 
     if (!fVerbose) {
         UniValue o(UniValue::VARR);
         for (CTxMemPool::txiter descendantIt : setDescendants) {
             o.push_back(descendantIt->GetTx().GetId().ToString());
         }
 
         return o;
     } else {
         UniValue o(UniValue::VOBJ);
         for (CTxMemPool::txiter descendantIt : setDescendants) {
             const CTxMemPoolEntry &e = *descendantIt;
             const TxId &_txid = e.GetTx().GetId();
             UniValue info(UniValue::VOBJ);
             entryToJSON(::g_mempool, info, e);
             o.pushKV(_txid.ToString(), info);
         }
         return o;
     }
 }
 
 static UniValue getmempoolentry(const Config &config,
                                 const JSONRPCRequest &request) {
     if (request.fHelp || request.params.size() != 1) {
         throw std::runtime_error(RPCHelpMan{
             "getmempoolentry",
             "\nReturns mempool data for given transaction\n",
             {
-                {"txid", RPCArg::Type::STR_HEX, /* opt */ false,
-                 /* default_val */ "",
+                {"txid", RPCArg::Type::STR_HEX, RPCArg::Optional::NO,
                  "The transaction id (must be in mempool)"},
             },
             RPCResult{"{                           (json object)\n" +
                       EntryDescriptionString() + "}\n"},
             RPCExamples{HelpExampleCli("getmempoolentry", "\"mytxid\"") +
                         HelpExampleRpc("getmempoolentry", "\"mytxid\"")},
         }
                                      .ToString());
     }
 
     TxId txid(ParseHashV(request.params[0], "parameter 1"));
 
     LOCK(g_mempool.cs);
 
     CTxMemPool::txiter it = g_mempool.mapTx.find(txid);
     if (it == g_mempool.mapTx.end()) {
         throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY,
                            "Transaction not in mempool");
     }
 
     const CTxMemPoolEntry &e = *it;
     UniValue info(UniValue::VOBJ);
     entryToJSON(::g_mempool, info, e);
     return info;
 }
 
 static UniValue getblockhash(const Config &config,
                              const JSONRPCRequest &request) {
     if (request.fHelp || request.params.size() != 1) {
         throw std::runtime_error(RPCHelpMan{
             "getblockhash",
             "\nReturns hash of block in best-block-chain at height "
             "provided.\n",
             {
-                {"height", RPCArg::Type::NUM, /* opt */ false,
-                 /* default_val */ "", "The height index"},
+                {"height", RPCArg::Type::NUM, RPCArg::Optional::NO,
+                 "The height index"},
             },
             RPCResult{"\"hash\"         (string) The block hash\n"},
             RPCExamples{HelpExampleCli("getblockhash", "1000") +
                         HelpExampleRpc("getblockhash", "1000")},
         }
                                      .ToString());
     }
 
     LOCK(cs_main);
 
     int nHeight = request.params[0].get_int();
     if (nHeight < 0 || nHeight > ::ChainActive().Height()) {
         throw JSONRPCError(RPC_INVALID_PARAMETER, "Block height out of range");
     }
 
     CBlockIndex *pblockindex = ::ChainActive()[nHeight];
     return pblockindex->GetBlockHash().GetHex();
 }
 
 static UniValue getblockheader(const Config &config,
                                const JSONRPCRequest &request) {
     if (request.fHelp || request.params.size() < 1 ||
         request.params.size() > 2) {
         throw std::runtime_error(RPCHelpMan{
             "getblockheader",
             "\nIf verbose is false, returns a string that is "
             "serialized, hex-encoded data for blockheader 'hash'.\n"
             "If verbose is true, returns an Object with information "
             "about blockheader <hash>.\n",
             {
-                {"blockhash", RPCArg::Type::STR_HEX, /* opt */ false,
-                 /* default_val */ "", "The block hash"},
-                {"verbose", RPCArg::Type::BOOL, /* opt */ true,
-                 /* default_val */ "true",
+                {"blockhash", RPCArg::Type::STR_HEX, RPCArg::Optional::NO,
+                 "The block hash"},
+                {"verbose", RPCArg::Type::BOOL, /* default */ "true",
                  "true for a json object, false for the hex-encoded data"},
             },
             {
                 RPCResult{
                     "for verbose = true",
                     "{\n"
                     "  \"hash\" : \"hash\",     (string) the block hash (same "
                     "as provided)\n"
                     "  \"confirmations\" : n,   (numeric) The number of "
                     "confirmations, or -1 if the block is not on the main "
                     "chain\n"
                     "  \"height\" : n,          (numeric) The block height or "
                     "index\n"
                     "  \"version\" : n,         (numeric) The block version\n"
                     "  \"versionHex\" : \"00000000\", (string) The block "
                     "version formatted in hexadecimal\n"
                     "  \"merkleroot\" : \"xxxx\", (string) The merkle root\n"
                     "  \"time\" : ttt,          (numeric) The block time in "
                     "seconds since epoch (Jan 1 1970 GMT)\n"
                     "  \"mediantime\" : ttt,    (numeric) The median block "
                     "time in seconds since epoch (Jan 1 1970 GMT)\n"
                     "  \"nonce\" : n,           (numeric) The nonce\n"
                     "  \"bits\" : \"1d00ffff\", (string) The bits\n"
                     "  \"difficulty\" : x.xxx,  (numeric) The difficulty\n"
                     "  \"chainwork\" : \"0000...1f3\"     (string) Expected "
                     "number of hashes required to produce the current chain "
                     "(in hex)\n"
                     "  \"nTx\" : n,             (numeric) The number of "
                     "transactions in the block.\n"
                     "  \"previousblockhash\" : \"hash\",  (string) The hash of "
                     "the previous block\n"
                     "  \"nextblockhash\" : \"hash\",      (string) The hash of "
                     "the next block\n"
                     "}\n"},
                 RPCResult{"for verbose=false",
                           "\"data\"             (string) A string that is "
                           "serialized, hex-encoded data for block 'hash'.\n"},
             },
             RPCExamples{HelpExampleCli("getblockheader",
                                        "\"00000000c937983704a73af28acdec3"
                                        "7b049d214adbda81d7e2a3dd146f6ed09"
                                        "\"") +
                         HelpExampleRpc("getblockheader",
                                        "\"00000000c937983704a73af28acdec3"
                                        "7b049d214adbda81d7e2a3dd146f6ed09"
                                        "\"")},
         }
                                      .ToString());
     }
 
     BlockHash hash(ParseHashV(request.params[0], "hash"));
 
     bool fVerbose = true;
     if (!request.params[1].isNull()) {
         fVerbose = request.params[1].get_bool();
     }
 
     const CBlockIndex *pblockindex;
     const CBlockIndex *tip;
     {
         LOCK(cs_main);
         pblockindex = LookupBlockIndex(hash);
         tip = ::ChainActive().Tip();
     }
 
     if (!pblockindex) {
         throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Block not found");
     }
 
     if (!fVerbose) {
         CDataStream ssBlock(SER_NETWORK, PROTOCOL_VERSION);
         ssBlock << pblockindex->GetBlockHeader();
         std::string strHex = HexStr(ssBlock.begin(), ssBlock.end());
         return strHex;
     }
 
     return blockheaderToJSON(tip, pblockindex);
 }
 
 static CBlock GetBlockChecked(const Config &config,
                               const CBlockIndex *pblockindex) {
     CBlock block;
     if (IsBlockPruned(pblockindex)) {
         throw JSONRPCError(RPC_MISC_ERROR, "Block not available (pruned data)");
     }
 
     if (!ReadBlockFromDisk(block, pblockindex,
                            config.GetChainParams().GetConsensus())) {
         // Block not found on disk. This could be because we have the block
         // header in our index but don't have the block (for example if a
         // non-whitelisted node sends us an unrequested long chain of valid
         // blocks, we add the headers to our index, but don't accept the block).
         throw JSONRPCError(RPC_MISC_ERROR, "Block not found on disk");
     }
 
     return block;
 }
 
 static UniValue getblock(const Config &config, const JSONRPCRequest &request) {
     if (request.fHelp || request.params.size() < 1 ||
         request.params.size() > 2) {
         throw std::runtime_error(RPCHelpMan{
             "getblock",
             "\nIf verbosity is 0 or false, returns a string that is "
             "serialized, hex-encoded data for block 'hash'.\n"
             "If verbosity is 1 or true, returns an Object with information "
             "about block <hash>.\n"
             "If verbosity is 2, returns an Object with information about "
             "block <hash> and information about each transaction.\n",
             {
-                {"blockhash", RPCArg::Type::STR_HEX, /* opt */ false,
-                 /* default_val */ "", "The block hash"},
-                {"verbosity", RPCArg::Type::NUM, /* opt */ true,
-                 /* default_val */ "1",
+                {"blockhash", RPCArg::Type::STR_HEX, RPCArg::Optional::NO,
+                 "The block hash"},
+                {"verbosity", RPCArg::Type::NUM, /* default */ "1",
                  "0 for hex-encoded data, 1 for a json object, and 2 for "
                  "json object with transaction data"},
             },
             {
                 RPCResult{
                     "for verbosity = 0",
                     "\"data\"                   (string) A string that is "
                     "serialized, hex-encoded data for block 'hash'.\n"},
                 RPCResult{
                     "for verbosity = 1",
                     "{\n"
                     "  \"hash\" : \"hash\",       (string) The block hash "
                     "(same as provided)\n"
                     "  \"confirmations\" : n,   (numeric) The number of "
                     "confirmations, or -1 if the block is not on the main "
                     "chain\n"
                     "  \"size\" : n,            (numeric) The block size\n"
                     "  \"height\" : n,          (numeric) The block height or "
                     "index\n"
                     "  \"version\" : n,         (numeric) The block version\n"
                     "  \"versionHex\" : \"00000000\", (string) The block "
                     "version formatted in hexadecimal\n"
                     "  \"merkleroot\" : \"xxxx\", (string) The merkle root\n"
                     "  \"tx\" : [               (array of string) The "
                     "transaction ids\n"
                     "     \"transactionid\"     (string) The transaction id\n"
                     "     ,...\n"
                     "  ],\n"
                     "  \"time\" : ttt,          (numeric) The block time in "
                     "seconds since epoch (Jan 1 1970 GMT)\n"
                     "  \"mediantime\" : ttt,    (numeric) The median block "
                     "time in seconds since epoch (Jan 1 1970 GMT)\n"
                     "  \"nonce\" : n,           (numeric) The nonce\n"
                     "  \"bits\" : \"1d00ffff\",   (string) The bits\n"
                     "  \"difficulty\" : x.xxx,  (numeric) The difficulty\n"
                     "  \"chainwork\" : \"xxxx\",  (string) Expected number of "
                     "hashes required to produce the chain up to this block (in "
                     "hex)\n"
                     "  \"nTx\" : n,             (numeric) The number of "
                     "transactions in the block.\n"
                     "  \"previousblockhash\" : \"hash\",  (string) The hash of "
                     "the previous block\n"
                     "  \"nextblockhash\" : \"hash\"       (string) The hash of "
                     "the next block\n"
                     "}\n"},
                 RPCResult{
                     "for verbosity = 2",
                     "{\n"
                     "  ...,                   Same output as verbosity = 1\n"
                     "  \"tx\" : [               (array of Objects) The "
                     "transactions in the format of the getrawtransaction RPC; "
                     "different from verbosity = 1 \"tx\" result\n"
                     "    ...\n"
                     "  ],\n"
                     "  ...                    Same output as verbosity = 1\n"
                     "}\n"},
             },
             RPCExamples{HelpExampleCli("getblock",
                                        "\"00000000c937983704a73af28acdec37b049d"
                                        "214adbda81d7e2a3dd146f6ed09\"") +
                         HelpExampleRpc("getblock",
                                        "\"00000000c937983704a73af28acdec37b049d"
                                        "214adbda81d7e2a3dd146f6ed09\"")},
         }
                                      .ToString());
     }
 
     LOCK(cs_main);
 
     BlockHash hash(ParseHashV(request.params[0], "blockhash"));
 
     int verbosity = 1;
     if (!request.params[1].isNull()) {
         if (request.params[1].isNum()) {
             verbosity = request.params[1].get_int();
         } else {
             verbosity = request.params[1].get_bool() ? 1 : 0;
         }
     }
 
     const CBlockIndex *pblockindex = LookupBlockIndex(hash);
     if (!pblockindex) {
         throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Block not found");
     }
 
     const CBlock block = GetBlockChecked(config, pblockindex);
 
     if (verbosity <= 0) {
         CDataStream ssBlock(SER_NETWORK,
                             PROTOCOL_VERSION | RPCSerializationFlags());
         ssBlock << block;
         std::string strHex = HexStr(ssBlock.begin(), ssBlock.end());
         return strHex;
     }
 
     return blockToJSON(block, ::ChainActive().Tip(), pblockindex,
                        verbosity >= 2);
 }
 
 static UniValue pruneblockchain(const Config &config,
                                 const JSONRPCRequest &request) {
     if (request.fHelp || request.params.size() != 1) {
         throw std::runtime_error(RPCHelpMan{
             "pruneblockchain",
             "",
             {
-                {"height", RPCArg::Type::NUM, /* opt */ false,
-                 /* default_val */ "",
+                {"height", RPCArg::Type::NUM, RPCArg::Optional::NO,
                  "The block height to prune up to. May be set to a discrete "
                  "height, or a unix timestamp\n"
                  "                  to prune blocks whose block time is at "
                  "least 2 hours older than the provided timestamp."},
             },
             RPCResult{"n    (numeric) Height of the last block pruned.\n"},
             RPCExamples{HelpExampleCli("pruneblockchain", "1000") +
                         HelpExampleRpc("pruneblockchain", "1000")},
         }
                                      .ToString());
     }
 
     if (!fPruneMode) {
         throw JSONRPCError(
             RPC_MISC_ERROR,
             "Cannot prune blocks because node is not in prune mode.");
     }
 
     LOCK(cs_main);
 
     int heightParam = request.params[0].get_int();
     if (heightParam < 0) {
         throw JSONRPCError(RPC_INVALID_PARAMETER, "Negative block height.");
     }
 
     // Height value more than a billion is too high to be a block height, and
     // too low to be a block time (corresponds to timestamp from Sep 2001).
     if (heightParam > 1000000000) {
         // Add a 2 hour buffer to include blocks which might have had old
         // timestamps
         CBlockIndex *pindex =
             ::ChainActive().FindEarliestAtLeast(heightParam - TIMESTAMP_WINDOW);
         if (!pindex) {
             throw JSONRPCError(
                 RPC_INVALID_PARAMETER,
                 "Could not find block with at least the specified timestamp.");
         }
         heightParam = pindex->nHeight;
     }
 
     unsigned int height = (unsigned int)heightParam;
     unsigned int chainHeight = (unsigned int)::ChainActive().Height();
     if (chainHeight < config.GetChainParams().PruneAfterHeight()) {
         throw JSONRPCError(RPC_MISC_ERROR,
                            "Blockchain is too short for pruning.");
     } else if (height > chainHeight) {
         throw JSONRPCError(
             RPC_INVALID_PARAMETER,
             "Blockchain is shorter than the attempted prune height.");
     } else if (height > chainHeight - MIN_BLOCKS_TO_KEEP) {
         LogPrint(BCLog::RPC, "Attempt to prune blocks close to the tip. "
                              "Retaining the minimum number of blocks.\n");
         height = chainHeight - MIN_BLOCKS_TO_KEEP;
     }
 
     PruneBlockFilesManual(height);
     return uint64_t(height);
 }
 
 static UniValue gettxoutsetinfo(const Config &config,
                                 const JSONRPCRequest &request) {
     if (request.fHelp || request.params.size() != 0) {
         throw std::runtime_error(RPCHelpMan{
             "gettxoutsetinfo",
             "\nReturns statistics about the unspent transaction output set.\n"
             "Note this call may take some time.\n",
             {},
             RPCResult{
                 "{\n"
                 "  \"height\":n,     (numeric) The current block height "
                 "(index)\n"
                 "  \"bestblock\": \"hex\",   (string) the best block hash hex\n"
                 "  \"transactions\": n,      (numeric) The number of "
                 "transactions\n"
                 "  \"txouts\": n,            (numeric) The number of output "
                 "transactions\n"
                 "  \"bogosize\": n,          (numeric) A database-independent "
                 "metric for UTXO set size\n"
                 "  \"hash_serialized\": \"hash\",   (string) The serialized "
                 "hash\n"
                 "  \"disk_size\": n,         (numeric) The estimated size of "
                 "the chainstate on disk\n"
                 "  \"total_amount\": x.xxx          (numeric) The total "
                 "amount\n"
                 "}\n"},
             RPCExamples{HelpExampleCli("gettxoutsetinfo", "") +
                         HelpExampleRpc("gettxoutsetinfo", "")},
         }
                                      .ToString());
     }
 
     UniValue ret(UniValue::VOBJ);
 
     CCoinsStats stats;
     ::ChainstateActive().ForceFlushStateToDisk();
     if (GetUTXOStats(pcoinsdbview.get(), stats)) {
         ret.pushKV("height", int64_t(stats.nHeight));
         ret.pushKV("bestblock", stats.hashBlock.GetHex());
         ret.pushKV("transactions", int64_t(stats.nTransactions));
         ret.pushKV("txouts", int64_t(stats.nTransactionOutputs));
         ret.pushKV("bogosize", int64_t(stats.nBogoSize));
         ret.pushKV("hash_serialized", stats.hashSerialized.GetHex());
         ret.pushKV("disk_size", stats.nDiskSize);
         ret.pushKV("total_amount", ValueFromAmount(stats.nTotalAmount));
     } else {
         throw JSONRPCError(RPC_INTERNAL_ERROR, "Unable to read UTXO set");
     }
     return ret;
 }
 
 UniValue gettxout(const Config &config, const JSONRPCRequest &request) {
     if (request.fHelp || request.params.size() < 2 ||
         request.params.size() > 3) {
         throw std::runtime_error(RPCHelpMan{
             "gettxout",
             "\nReturns details about an unspent transaction output.\n",
             {
-                {"txid", RPCArg::Type::STR_HEX, /* opt */ false,
-                 /* default_val */ "", "The transaction id"},
-                {"n", RPCArg::Type::NUM, /* opt */ false,
-                 /* default_val */ "", "vout number"},
-                {"include_mempool", RPCArg::Type::BOOL, /* opt */ true,
-                 /* default_val */ "true",
+                {"txid", RPCArg::Type::STR_HEX, RPCArg::Optional::NO,
+                 "The transaction id"},
+                {"n", RPCArg::Type::NUM, RPCArg::Optional::NO, "vout number"},
+                {"include_mempool", RPCArg::Type::BOOL, /* default */ "true",
                  "Whether to include the mempool. Note that an unspent "
                  "output that is spent in the mempool won't appear."},
             },
             RPCResult{
                 "{\n"
                 "  \"bestblock\" : \"hash\",    (string) the block hash\n"
                 "  \"confirmations\" : n,       (numeric) The number of "
                 "confirmations\n"
                 "  \"value\" : x.xxx,           (numeric) The transaction "
                 "value in " +
                 CURRENCY_UNIT +
                 "\n"
                 "  \"scriptPubKey\" : {         (json object)\n"
                 "     \"asm\" : \"code\",       (string) \n"
                 "     \"hex\" : \"hex\",        (string) \n"
                 "     \"reqSigs\" : n,          (numeric) Number of required "
                 "signatures\n"
                 "     \"type\" : \"pubkeyhash\", (string) The type, eg "
                 "pubkeyhash\n"
                 "     \"addresses\" : [          (array of string) array of "
                 "bitcoin addresses\n"
                 "        \"address\"     (string) bitcoin address\n"
                 "        ,...\n"
                 "     ]\n"
                 "  },\n"
                 "  \"coinbase\" : true|false   (boolean) Coinbase or not\n"
                 "}\n"},
             RPCExamples{"\nGet unspent transactions\n" +
                         HelpExampleCli("listunspent", "") +
                         "\nView the details\n" +
                         HelpExampleCli("gettxout", "\"txid\" 1") +
                         "\nAs a JSON-RPC call\n" +
                         HelpExampleRpc("gettxout", "\"txid\", 1")},
         }
                                      .ToString());
     }
 
     LOCK(cs_main);
 
     UniValue ret(UniValue::VOBJ);
 
     TxId txid(ParseHashV(request.params[0], "txid"));
     int n = request.params[1].get_int();
     COutPoint out(txid, n);
     bool fMempool = true;
     if (!request.params[2].isNull()) {
         fMempool = request.params[2].get_bool();
     }
 
     Coin coin;
     if (fMempool) {
         LOCK(g_mempool.cs);
         CCoinsViewMemPool view(pcoinsTip.get(), g_mempool);
         if (!view.GetCoin(out, coin) || g_mempool.isSpent(out)) {
             return NullUniValue;
         }
     } else {
         if (!pcoinsTip->GetCoin(out, coin)) {
             return NullUniValue;
         }
     }
 
     const CBlockIndex *pindex = LookupBlockIndex(pcoinsTip->GetBestBlock());
     ret.pushKV("bestblock", pindex->GetBlockHash().GetHex());
     if (coin.GetHeight() == MEMPOOL_HEIGHT) {
         ret.pushKV("confirmations", 0);
     } else {
         ret.pushKV("confirmations",
                    int64_t(pindex->nHeight - coin.GetHeight() + 1));
     }
     ret.pushKV("value", ValueFromAmount(coin.GetTxOut().nValue));
     UniValue o(UniValue::VOBJ);
     ScriptPubKeyToUniv(coin.GetTxOut().scriptPubKey, o, true);
     ret.pushKV("scriptPubKey", o);
     ret.pushKV("coinbase", coin.IsCoinBase());
 
     return ret;
 }
 
 static UniValue verifychain(const Config &config,
                             const JSONRPCRequest &request) {
     int nCheckLevel = gArgs.GetArg("-checklevel", DEFAULT_CHECKLEVEL);
     int nCheckDepth = gArgs.GetArg("-checkblocks", DEFAULT_CHECKBLOCKS);
     if (request.fHelp || request.params.size() > 2) {
         throw std::runtime_error(RPCHelpMan{
             "verifychain",
             "\nVerifies blockchain database.\n",
             {
-                {"checklevel", RPCArg::Type::NUM, /* opt */ true,
-                 /* default_val */ strprintf("%d, range=0-4", nCheckLevel),
+                {"checklevel", RPCArg::Type::NUM,
+                 /* default */ strprintf("%d, range=0-4", nCheckLevel),
                  "How thorough the block verification is."},
-                {"nblocks", RPCArg::Type::NUM, /* opt */ true,
-                 /* default_val */ strprintf("%d, 0=all", nCheckDepth),
+                {"nblocks", RPCArg::Type::NUM,
+                 /* default */ strprintf("%d, 0=all", nCheckDepth),
                  "The number of blocks to check."},
             },
             RPCResult{"true|false       (boolean) Verified or not\n"},
             RPCExamples{HelpExampleCli("verifychain", "") +
                         HelpExampleRpc("verifychain", "")},
         }
                                      .ToString());
     }
 
     LOCK(cs_main);
 
     if (!request.params[0].isNull()) {
         nCheckLevel = request.params[0].get_int();
     }
     if (!request.params[1].isNull()) {
         nCheckDepth = request.params[1].get_int();
     }
 
     return CVerifyDB().VerifyDB(config, pcoinsTip.get(), nCheckLevel,
                                 nCheckDepth);
 }
 
 static void BIP9SoftForkDescPushBack(UniValue &softforks,
                                      const Consensus::Params &consensusParams,
                                      Consensus::DeploymentPos id)
     EXCLUSIVE_LOCKS_REQUIRED(cs_main) {
     // For BIP9 deployments.
     // Deployments (e.g. testdummy) with timeout value before Jan 1, 2009 are
     // hidden. A timeout value of 0 guarantees a softfork will never be
     // activated. This is used when merging logic to implement a proposed
     // softfork without a specified deployment schedule.
     if (consensusParams.vDeployments[id].nTimeout <= 1230768000) {
         return;
     }
 
     UniValue bip9(UniValue::VOBJ);
     const ThresholdState thresholdState =
         VersionBitsTipState(consensusParams, id);
     switch (thresholdState) {
         case ThresholdState::DEFINED:
             bip9.pushKV("status", "defined");
             break;
         case ThresholdState::STARTED:
             bip9.pushKV("status", "started");
             break;
         case ThresholdState::LOCKED_IN:
             bip9.pushKV("status", "locked_in");
             break;
         case ThresholdState::ACTIVE:
             bip9.pushKV("status", "active");
             break;
         case ThresholdState::FAILED:
             bip9.pushKV("status", "failed");
             break;
     }
     if (ThresholdState::STARTED == thresholdState) {
         bip9.pushKV("bit", consensusParams.vDeployments[id].bit);
     }
     bip9.pushKV("start_time", consensusParams.vDeployments[id].nStartTime);
     bip9.pushKV("timeout", consensusParams.vDeployments[id].nTimeout);
     int64_t since_height = VersionBitsTipStateSinceHeight(consensusParams, id);
     bip9.pushKV("since", since_height);
     if (ThresholdState::STARTED == thresholdState) {
         UniValue statsUV(UniValue::VOBJ);
         BIP9Stats statsStruct = VersionBitsTipStatistics(consensusParams, id);
         statsUV.pushKV("period", statsStruct.period);
         statsUV.pushKV("threshold", statsStruct.threshold);
         statsUV.pushKV("elapsed", statsStruct.elapsed);
         statsUV.pushKV("count", statsStruct.count);
         statsUV.pushKV("possible", statsStruct.possible);
         bip9.pushKV("statistics", statsUV);
     }
 
     UniValue rv(UniValue::VOBJ);
     rv.pushKV("type", "bip9");
     rv.pushKV("bip9", bip9);
     if (ThresholdState::ACTIVE == thresholdState) {
         rv.pushKV("height", since_height);
     }
     rv.pushKV("active", ThresholdState::ACTIVE == thresholdState);
 
     softforks.pushKV(VersionBitsDeploymentInfo[id].name, rv);
 }
 
 UniValue getblockchaininfo(const Config &config,
                            const JSONRPCRequest &request) {
     if (request.fHelp || request.params.size() != 0) {
         throw std::runtime_error(RPCHelpMan{
             "getblockchaininfo",
             "Returns an object containing various state info "
             "regarding blockchain processing.\n",
             {},
             RPCResult{
                 "{\n"
                 "  \"chain\": \"xxxx\",              (string) current network "
                 "name as defined in BIP70 (main, test, regtest)\n"
                 "  \"blocks\": xxxxxx,             (numeric) the current "
                 "number of blocks processed in the server\n"
                 "  \"headers\": xxxxxx,            (numeric) the current "
                 "number of headers we have validated\n"
                 "  \"bestblockhash\": \"...\",       (string) the hash of the "
                 "currently best block\n"
                 "  \"difficulty\": xxxxxx,         (numeric) the current "
                 "difficulty\n"
                 "  \"mediantime\": xxxxxx,         (numeric) median time for "
                 "the current best block\n"
                 "  \"verificationprogress\": xxxx, (numeric) estimate of "
                 "verification progress [0..1]\n"
                 "  \"initialblockdownload\": xxxx, (bool) (debug information) "
                 "estimate of whether this node is in Initial Block Download "
                 "mode.\n"
                 "  \"chainwork\": \"xxxx\"           (string) total amount of "
                 "work in active chain, in hexadecimal\n"
                 "  \"size_on_disk\": xxxxxx,       (numeric) the estimated "
                 "size of the block and undo files on disk\n"
                 "  \"pruned\": xx,                 (boolean) if the blocks are "
                 "subject to pruning\n"
                 "  \"pruneheight\": xxxxxx,        (numeric) lowest-height "
                 "complete block stored (only present if pruning is enabled)\n"
                 "  \"automatic_pruning\": xx,      (boolean) whether automatic "
                 "pruning is enabled (only present if pruning is enabled)\n"
                 "  \"prune_target_size\": xxxxxx,  (numeric) the target size "
                 "used by pruning (only present if automatic pruning is "
                 "enabled)\n"
                 "  \"softforks\": {                (object) status of "
                 "softforks in progress\n"
                 "    \"xxxx\" : {                  (string) name of the "
                 "softfork\n"
                 "      \"type\" : \"bip9\",        (string) currently only set "
                 "to \"bip9\"\n"
                 "      \"bip9\" : {                (object) status of bip9 "
                 "softforks (only for \"bip9\" type)\n"
                 "        \"status\": \"xxxx\",     (string) one of "
                 "\"defined\", \"started\", \"locked_in\", \"active\", "
                 "\"failed\"\n"
                 "        \"bit\": xx,              (numeric) the bit (0-28) in "
                 "the block version field used to signal this softfork (only "
                 "for \"started\" status)\n"
                 "        \"startTime\": xx,        (numeric) the minimum "
                 "median time past of a block at which the bit gains its "
                 "meaning\n"
                 "        \"timeout\": xx,          (numeric) the median time "
                 "past of a block at which the deployment is considered failed "
                 "if not "
                 "yet locked in\n"
                 "        \"since\": xx,            (numeric) height of the "
                 "first block to which the status applies\n"
                 "        \"statistics\": {         (object) numeric statistics "
                 "about BIP9 signalling for a softfork (only for \"started\" "
                 "status)\n"
                 "          \"period\": xx,         (numeric) the length in "
                 "blocks of the BIP9 signalling period \n"
                 "          \"threshold\": xx,      (numeric) the number of "
                 "blocks with the version bit set required to activate the "
                 "feature \n"
                 "          \"elapsed\": xx,        (numeric) the number of "
                 "blocks elapsed since the beginning of the current period \n"
                 "          \"count\": xx,          (numeric) the number of "
                 "blocks with the version bit set in the current period \n"
                 "          \"possible\": xx        (boolean) returns false if "
                 "there are not enough blocks left in this period to pass "
                 "activation threshold\n"
                 "        },\n"
                 "        \"active\": xx,           (boolean) true if the rules "
                 "are enforced for the mempool and the next block\n"
                 "      }\n"
                 "    }\n"
                 "  }\n"
                 "  \"warnings\" : \"...\",           (string) any network and "
                 "blockchain warnings.\n"
                 "}\n"},
             RPCExamples{HelpExampleCli("getblockchaininfo", "") +
                         HelpExampleRpc("getblockchaininfo", "")},
         }
                                      .ToString());
     }
 
     LOCK(cs_main);
 
     const CChainParams &chainparams = config.GetChainParams();
 
     const CBlockIndex *tip = ::ChainActive().Tip();
     UniValue obj(UniValue::VOBJ);
     obj.pushKV("chain", chainparams.NetworkIDString());
     obj.pushKV("blocks", int(::ChainActive().Height()));
     obj.pushKV("headers", pindexBestHeader ? pindexBestHeader->nHeight : -1);
     obj.pushKV("bestblockhash", tip->GetBlockHash().GetHex());
     obj.pushKV("difficulty", double(GetDifficulty(tip)));
     obj.pushKV("mediantime", int64_t(tip->GetMedianTimePast()));
     obj.pushKV("verificationprogress",
                GuessVerificationProgress(Params().TxData(), tip));
     obj.pushKV("initialblockdownload",
                ::ChainstateActive().IsInitialBlockDownload());
     obj.pushKV("chainwork", tip->nChainWork.GetHex());
     obj.pushKV("size_on_disk", CalculateCurrentUsage());
     obj.pushKV("pruned", fPruneMode);
 
     if (fPruneMode) {
         const CBlockIndex *block = tip;
         assert(block);
         while (block->pprev && (block->pprev->nStatus.hasData())) {
             block = block->pprev;
         }
 
         obj.pushKV("pruneheight", block->nHeight);
 
         // if 0, execution bypasses the whole if block.
         bool automatic_pruning = (gArgs.GetArg("-prune", 0) != 1);
         obj.pushKV("automatic_pruning", automatic_pruning);
         if (automatic_pruning) {
             obj.pushKV("prune_target_size", nPruneTarget);
         }
     }
 
     UniValue softforks(UniValue::VOBJ);
     for (int i = 0; i < (int)Consensus::MAX_VERSION_BITS_DEPLOYMENTS; i++) {
         BIP9SoftForkDescPushBack(softforks, chainparams.GetConsensus(),
                                  Consensus::DeploymentPos(i));
     }
     obj.pushKV("softforks", softforks);
 
     obj.pushKV("warnings", GetWarnings("statusbar"));
     return obj;
 }
 
 /** Comparison function for sorting the getchaintips heads.  */
 struct CompareBlocksByHeight {
     bool operator()(const CBlockIndex *a, const CBlockIndex *b) const {
         // Make sure that unequal blocks with the same height do not compare
         // equal. Use the pointers themselves to make a distinction.
         if (a->nHeight != b->nHeight) {
             return (a->nHeight > b->nHeight);
         }
 
         return a < b;
     }
 };
 
 static UniValue getchaintips(const Config &config,
                              const JSONRPCRequest &request) {
     if (request.fHelp || request.params.size() != 0) {
         throw std::runtime_error(RPCHelpMan{
             "getchaintips",
             "Return information about all known tips in the block tree, "
             "including the main chain as well as orphaned branches.\n",
             {},
             RPCResult{
                 "[\n"
                 "  {\n"
                 "    \"height\": xxxx,         (numeric) height of the chain "
                 "tip\n"
                 "    \"hash\": \"xxxx\",         (string) block hash of the "
                 "tip\n"
                 "    \"branchlen\": 0          (numeric) zero for main chain\n"
                 "    \"status\": \"active\"      (string) \"active\" for the "
                 "main chain\n"
                 "  },\n"
                 "  {\n"
                 "    \"height\": xxxx,\n"
                 "    \"hash\": \"xxxx\",\n"
                 "    \"branchlen\": 1          (numeric) length of branch "
                 "connecting the tip to the main chain\n"
                 "    \"status\": \"xxxx\"        (string) status of the chain "
                 "(active, valid-fork, valid-headers, headers-only, invalid)\n"
                 "  }\n"
                 "]\n"
                 "Possible values for status:\n"
                 "1.  \"invalid\"               This branch contains at least "
                 "one invalid block\n"
                 "2.  \"parked\"                This branch contains at least "
                 "one parked block\n"
                 "3.  \"headers-only\"          Not all blocks for this branch "
                 "are available, but the headers are valid\n"
                 "4.  \"valid-headers\"         All blocks are available for "
                 "this branch, but they were never fully validated\n"
                 "5.  \"valid-fork\"            This branch is not part of the "
                 "active chain, but is fully validated\n"
                 "6.  \"active\"                This is the tip of the active "
                 "main chain, which is certainly valid\n"},
             RPCExamples{HelpExampleCli("getchaintips", "") +
                         HelpExampleRpc("getchaintips", "")},
         }
                                      .ToString());
     }
 
     LOCK(cs_main);
 
     /**
      * Idea:  the set of chain tips is ::ChainActive().tip, plus orphan blocks
      * which do not have another orphan building off of them. Algorithm:
      *  - Make one pass through mapBlockIndex, picking out the orphan blocks,
      * and also storing a set of the orphan block's pprev pointers.
      *  - Iterate through the orphan blocks. If the block isn't pointed to by
      * another orphan, it is a chain tip.
      *  - add ::ChainActive().Tip()
      */
     std::set<const CBlockIndex *, CompareBlocksByHeight> setTips;
     std::set<const CBlockIndex *> setOrphans;
     std::set<const CBlockIndex *> setPrevs;
 
     for (const std::pair<const BlockHash, CBlockIndex *> &item :
          mapBlockIndex) {
         if (!::ChainActive().Contains(item.second)) {
             setOrphans.insert(item.second);
             setPrevs.insert(item.second->pprev);
         }
     }
 
     for (std::set<const CBlockIndex *>::iterator it = setOrphans.begin();
          it != setOrphans.end(); ++it) {
         if (setPrevs.erase(*it) == 0) {
             setTips.insert(*it);
         }
     }
 
     // Always report the currently active tip.
     setTips.insert(::ChainActive().Tip());
 
     /* Construct the output array.  */
     UniValue res(UniValue::VARR);
     for (const CBlockIndex *block : setTips) {
         UniValue obj(UniValue::VOBJ);
         obj.pushKV("height", block->nHeight);
         obj.pushKV("hash", block->phashBlock->GetHex());
 
         const int branchLen =
             block->nHeight - ::ChainActive().FindFork(block)->nHeight;
         obj.pushKV("branchlen", branchLen);
 
         std::string status;
         if (::ChainActive().Contains(block)) {
             // This block is part of the currently active chain.
             status = "active";
         } else if (block->nStatus.isInvalid()) {
             // This block or one of its ancestors is invalid.
             status = "invalid";
         } else if (block->nStatus.isOnParkedChain()) {
             // This block or one of its ancestors is parked.
             status = "parked";
         } else if (!block->HaveTxsDownloaded()) {
             // This block cannot be connected because full block data for it or
             // one of its parents is missing.
             status = "headers-only";
         } else if (block->IsValid(BlockValidity::SCRIPTS)) {
             // This block is fully validated, but no longer part of the active
             // chain. It was probably the active block once, but was
             // reorganized.
             status = "valid-fork";
         } else if (block->IsValid(BlockValidity::TREE)) {
             // The headers for this block are valid, but it has not been
             // validated. It was probably never part of the most-work chain.
             status = "valid-headers";
         } else {
             // No clue.
             status = "unknown";
         }
         obj.pushKV("status", status);
 
         res.push_back(obj);
     }
 
     return res;
 }
 
 UniValue MempoolInfoToJSON(const CTxMemPool &pool) {
     UniValue ret(UniValue::VOBJ);
     ret.pushKV("loaded", pool.IsLoaded());
     ret.pushKV("size", (int64_t)pool.size());
     ret.pushKV("bytes", (int64_t)pool.GetTotalTxSize());
     ret.pushKV("usage", (int64_t)pool.DynamicMemoryUsage());
     size_t maxmempool =
         gArgs.GetArg("-maxmempool", DEFAULT_MAX_MEMPOOL_SIZE) * 1000000;
     ret.pushKV("maxmempool", (int64_t)maxmempool);
     ret.pushKV(
         "mempoolminfee",
         ValueFromAmount(std::max(pool.GetMinFee(maxmempool), ::minRelayTxFee)
                             .GetFeePerK()));
     ret.pushKV("minrelaytxfee", ValueFromAmount(::minRelayTxFee.GetFeePerK()));
 
     return ret;
 }
 
 static UniValue getmempoolinfo(const Config &config,
                                const JSONRPCRequest &request) {
     if (request.fHelp || request.params.size() != 0) {
         throw std::runtime_error(RPCHelpMan{
             "getmempoolinfo",
             "\nReturns details on the active state of the TX memory "
             "pool.\n",
             {},
             RPCResult{
                 "{\n"
                 "  \"loaded\": true|false         (boolean) True if the "
                 "mempool is fully loaded\n"
                 "  \"size\": xxxxx,               (numeric) Current tx count\n"
                 "  \"bytes\": xxxxx,              (numeric) Transaction size.\n"
                 "  \"usage\": xxxxx,              (numeric) Total memory usage "
                 "for the mempool\n"
                 "  \"maxmempool\": xxxxx,         (numeric) Maximum memory "
                 "usage for the mempool\n"
                 "  \"mempoolminfee\": xxxxx       (numeric) Minimum fee rate "
                 "in " +
                 CURRENCY_UNIT +
                 "/kB for tx to be accepted. Is the maximum of minrelaytxfee "
                 "and minimum mempool fee\n"
                 "  \"minrelaytxfee\": xxxxx       (numeric) Current minimum "
                 "relay fee for transactions\n"
                 "}\n"},
             RPCExamples{HelpExampleCli("getmempoolinfo", "") +
                         HelpExampleRpc("getmempoolinfo", "")},
         }
                                      .ToString());
     }
 
     return MempoolInfoToJSON(::g_mempool);
 }
 
 static UniValue preciousblock(const Config &config,
                               const JSONRPCRequest &request) {
     if (request.fHelp || request.params.size() != 1) {
         throw std::runtime_error(RPCHelpMan{
             "preciousblock",
             "\nTreats a block as if it were received before others "
             "with the same work.\n"
             "\nA later preciousblock call can override the effect "
             "of an earlier one.\n"
             "\nThe effects of preciousblock are not retained across "
             "restarts.\n",
             {
-                {"blockhash", RPCArg::Type::STR_HEX, /* opt */ false,
-                 /* default_val */ "",
+                {"blockhash", RPCArg::Type::STR_HEX, RPCArg::Optional::NO,
                  "the hash of the block to mark as precious"},
             },
             RPCResults{},
             RPCExamples{HelpExampleCli("preciousblock", "\"blockhash\"") +
                         HelpExampleRpc("preciousblock", "\"blockhash\"")},
         }
                                      .ToString());
     }
 
     BlockHash hash(ParseHashV(request.params[0], "blockhash"));
     CBlockIndex *pblockindex;
 
     {
         LOCK(cs_main);
         pblockindex = LookupBlockIndex(hash);
         if (!pblockindex) {
             throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Block not found");
         }
     }
 
     CValidationState state;
     PreciousBlock(config, state, pblockindex);
 
     if (!state.IsValid()) {
         throw JSONRPCError(RPC_DATABASE_ERROR, state.GetRejectReason());
     }
 
     return NullUniValue;
 }
 
 UniValue finalizeblock(const Config &config, const JSONRPCRequest &request) {
     if (request.fHelp || request.params.size() != 1) {
         throw std::runtime_error(RPCHelpMan{
             "finalizeblock",
             "\nTreats a block as final. It cannot be reorged. Any chain\n"
             "that does not contain this block is invalid. Used on a less\n"
             "work chain, it can effectively PUTS YOU OUT OF CONSENSUS.\n"
             "USE WITH CAUTION!\n",
             {
-                {"blockhash", RPCArg::Type::STR_HEX, /* opt */ false,
-                 /* default_val */ "",
+                {"blockhash", RPCArg::Type::STR_HEX, RPCArg::Optional::NO,
                  "the hash of the block to mark as invalid"},
             },
             RPCResults{},
             RPCExamples{HelpExampleCli("invalidateblock", "\"blockhash\"") +
                         HelpExampleRpc("invalidateblock", "\"blockhash\"")},
         }
                                      .ToString());
     }
 
     std::string strHash = request.params[0].get_str();
     BlockHash hash(uint256S(strHash));
     CValidationState state;
 
     {
         LOCK(cs_main);
         CBlockIndex *pblockindex = LookupBlockIndex(hash);
         if (!pblockindex) {
             throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Block not found");
         }
 
         FinalizeBlockAndInvalidate(config, state, pblockindex);
     }
 
     if (state.IsValid()) {
         ActivateBestChain(config, state);
     }
 
     if (!state.IsValid()) {
         throw JSONRPCError(RPC_DATABASE_ERROR, FormatStateMessage(state));
     }
 
     return NullUniValue;
 }
 
 static UniValue invalidateblock(const Config &config,
                                 const JSONRPCRequest &request) {
     if (request.fHelp || request.params.size() != 1) {
         throw std::runtime_error(RPCHelpMan{
             "invalidateblock",
             "\nPermanently marks a block as invalid, as if it "
             "violated a consensus rule.\n",
             {
-                {"blockhash", RPCArg::Type::STR_HEX, /* opt */ false,
-                 /* default_val */ "",
+                {"blockhash", RPCArg::Type::STR_HEX, RPCArg::Optional::NO,
                  "the hash of the block to mark as invalid"},
             },
             RPCResults{},
             RPCExamples{HelpExampleCli("invalidateblock", "\"blockhash\"") +
                         HelpExampleRpc("invalidateblock", "\"blockhash\"")},
         }
                                      .ToString());
     }
 
     const BlockHash hash(ParseHashV(request.params[0], "blockhash"));
     CValidationState state;
 
     CBlockIndex *pblockindex;
     {
         LOCK(cs_main);
         pblockindex = LookupBlockIndex(hash);
         if (!pblockindex) {
             throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Block not found");
         }
     }
     InvalidateBlock(config, state, pblockindex);
 
     if (state.IsValid()) {
         ActivateBestChain(config, state);
     }
 
     if (!state.IsValid()) {
         throw JSONRPCError(RPC_DATABASE_ERROR, FormatStateMessage(state));
     }
 
     return NullUniValue;
 }
 
 UniValue parkblock(const Config &config, const JSONRPCRequest &request) {
     if (request.fHelp || request.params.size() != 1) {
         throw std::runtime_error(RPCHelpMan{
             "parkblock",
             "\nMarks a block as parked.\n",
             {
-                {"blockhash", RPCArg::Type::STR_HEX, /* opt */ false,
-                 /* default_val */ "", "the hash of the block to park"},
+                {"blockhash", RPCArg::Type::STR_HEX, RPCArg::Optional::NO,
+                 "the hash of the block to park"},
             },
             RPCResults{},
             RPCExamples{HelpExampleCli("parkblock", "\"blockhash\"") +
                         HelpExampleRpc("parkblock", "\"blockhash\"")},
         }
                                      .ToString());
     }
 
     const std::string strHash = request.params[0].get_str();
     const BlockHash hash(uint256S(strHash));
     CValidationState state;
 
     CBlockIndex *pblockindex;
     {
         LOCK(cs_main);
         if (mapBlockIndex.count(hash) == 0) {
             throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Block not found");
         }
 
         pblockindex = mapBlockIndex[hash];
     }
     ParkBlock(config, state, pblockindex);
 
     if (state.IsValid()) {
         ActivateBestChain(config, state);
     }
 
     if (!state.IsValid()) {
         throw JSONRPCError(RPC_DATABASE_ERROR, state.GetRejectReason());
     }
 
     return NullUniValue;
 }
 
 static UniValue reconsiderblock(const Config &config,
                                 const JSONRPCRequest &request) {
     if (request.fHelp || request.params.size() != 1) {
         throw std::runtime_error(RPCHelpMan{
             "reconsiderblock",
             "\nRemoves invalidity status of a block and its descendants, "
             "reconsider them for activation.\n"
             "This can be used to undo the effects of invalidateblock.\n",
             {
-                {"blockhash", RPCArg::Type::STR_HEX, /* opt */ false,
-                 /* default_val */ "", "the hash of the block to reconsider"},
+                {"blockhash", RPCArg::Type::STR_HEX, RPCArg::Optional::NO,
+                 "the hash of the block to reconsider"},
             },
             RPCResults{},
             RPCExamples{HelpExampleCli("reconsiderblock", "\"blockhash\"") +
                         HelpExampleRpc("reconsiderblock", "\"blockhash\"")},
         }
                                      .ToString());
     }
 
     const BlockHash hash(ParseHashV(request.params[0], "blockhash"));
 
     {
         LOCK(cs_main);
         CBlockIndex *pblockindex = LookupBlockIndex(hash);
         if (!pblockindex) {
             throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Block not found");
         }
 
         ResetBlockFailureFlags(pblockindex);
     }
 
     CValidationState state;
     ActivateBestChain(config, state);
 
     if (!state.IsValid()) {
         throw JSONRPCError(RPC_DATABASE_ERROR, FormatStateMessage(state));
     }
 
     return NullUniValue;
 }
 
 UniValue unparkblock(const Config &config, const JSONRPCRequest &request) {
     if (request.fHelp || request.params.size() != 1) {
         throw std::runtime_error(RPCHelpMan{
             "unparkblock",
             "\nRemoves parked status of a block and its descendants, "
             "reconsider them for activation.\n"
             "This can be used to undo the effects of parkblock.\n",
             {
-                {"blockhash", RPCArg::Type::STR_HEX, /* opt */ false,
-                 /* default_val */ "", "the hash of the block to unpark"},
+                {"blockhash", RPCArg::Type::STR_HEX, RPCArg::Optional::NO,
+                 "the hash of the block to unpark"},
             },
             RPCResults{},
             RPCExamples{HelpExampleCli("unparkblock", "\"blockhash\"") +
                         HelpExampleRpc("unparkblock", "\"blockhash\"")},
         }
                                      .ToString());
     }
 
     const std::string strHash = request.params[0].get_str();
     const BlockHash hash(uint256S(strHash));
 
     {
         LOCK(cs_main);
         if (mapBlockIndex.count(hash) == 0) {
             throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Block not found");
         }
 
         CBlockIndex *pblockindex = mapBlockIndex[hash];
         UnparkBlockAndChildren(pblockindex);
     }
 
     CValidationState state;
     ActivateBestChain(config, state);
 
     if (!state.IsValid()) {
         throw JSONRPCError(RPC_DATABASE_ERROR, state.GetRejectReason());
     }
 
     return NullUniValue;
 }
 
 static UniValue getchaintxstats(const Config &config,
                                 const JSONRPCRequest &request) {
     if (request.fHelp || request.params.size() > 2) {
         throw std::runtime_error(RPCHelpMan{
             "getchaintxstats",
             "\nCompute statistics about the total number and rate "
             "of transactions in the chain.\n",
             {
-                {"nblocks", RPCArg::Type::NUM, /* opt */ true,
-                 /* default_val */ "one month",
+                {"nblocks", RPCArg::Type::NUM, /* default */ "one month",
                  "Size of the window in number of blocks"},
-                {"blockhash", RPCArg::Type::STR_HEX, /* opt */ true,
-                 /* default_val */ "chain tip",
+                {"blockhash", RPCArg::Type::STR_HEX, /* default */ "chain tip",
                  "The hash of the block that ends the window."},
             },
             RPCResult{
                 "{\n"
                 "  \"time\": xxxxx,                         (numeric) The "
                 "timestamp for the final block in the window in UNIX format.\n"
                 "  \"txcount\": xxxxx,                      (numeric) The "
                 "total number of transactions in the chain up to that point.\n"
                 "  \"window_final_block_hash\": \"...\",      (string) The "
                 "hash of the final block in the window.\n"
                 "  \"window_block_count\": xxxxx,           (numeric) Size of "
                 "the window in number of blocks.\n"
                 "  \"window_tx_count\": xxxxx,              (numeric) The "
                 "number of transactions in the window. Only returned if "
                 "\"window_block_count\" is > 0.\n"
                 "  \"window_interval\": xxxxx,              (numeric) The "
                 "elapsed time in the window in seconds. Only returned if "
                 "\"window_block_count\" is > 0.\n"
                 "  \"txrate\": x.xx,                        (numeric) The "
                 "average rate of transactions per second in the window. Only "
                 "returned if \"window_interval\" is > 0.\n"
                 "}\n"},
             RPCExamples{HelpExampleCli("getchaintxstats", "") +
                         HelpExampleRpc("getchaintxstats", "2016")},
         }
                                      .ToString());
     }
 
     const CBlockIndex *pindex;
 
     // By default: 1 month
     int blockcount = 30 * 24 * 60 * 60 /
                      config.GetChainParams().GetConsensus().nPowTargetSpacing;
 
     if (request.params[1].isNull()) {
         LOCK(cs_main);
         pindex = ::ChainActive().Tip();
     } else {
         BlockHash hash(ParseHashV(request.params[1], "blockhash"));
         LOCK(cs_main);
         pindex = LookupBlockIndex(hash);
         if (!pindex) {
             throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Block not found");
         }
         if (!::ChainActive().Contains(pindex)) {
             throw JSONRPCError(RPC_INVALID_PARAMETER,
                                "Block is not in main chain");
         }
     }
 
     assert(pindex != nullptr);
 
     if (request.params[0].isNull()) {
         blockcount = std::max(0, std::min(blockcount, pindex->nHeight - 1));
     } else {
         blockcount = request.params[0].get_int();
 
         if (blockcount < 0 ||
             (blockcount > 0 && blockcount >= pindex->nHeight)) {
             throw JSONRPCError(RPC_INVALID_PARAMETER, "Invalid block count: "
                                                       "should be between 0 and "
                                                       "the block's height - 1");
         }
     }
 
     const CBlockIndex *pindexPast =
         pindex->GetAncestor(pindex->nHeight - blockcount);
     int nTimeDiff =
         pindex->GetMedianTimePast() - pindexPast->GetMedianTimePast();
     int nTxDiff = pindex->nChainTx - pindexPast->nChainTx;
 
     UniValue ret(UniValue::VOBJ);
     ret.pushKV("time", int64_t(pindex->nTime));
     ret.pushKV("txcount", int64_t(pindex->nChainTx));
     ret.pushKV("window_final_block_hash", pindex->GetBlockHash().GetHex());
     ret.pushKV("window_block_count", blockcount);
     if (blockcount > 0) {
         ret.pushKV("window_tx_count", nTxDiff);
         ret.pushKV("window_interval", nTimeDiff);
         if (nTimeDiff > 0) {
             ret.pushKV("txrate", double(nTxDiff) / nTimeDiff);
         }
     }
 
     return ret;
 }
 
 template <typename T>
 static T CalculateTruncatedMedian(std::vector<T> &scores) {
     size_t size = scores.size();
     if (size == 0) {
         return T();
     }
 
     std::sort(scores.begin(), scores.end());
     if (size % 2 == 0) {
         return (scores[size / 2 - 1] + scores[size / 2]) / 2;
     } else {
         return scores[size / 2];
     }
 }
 
 template <typename T> static inline bool SetHasKeys(const std::set<T> &set) {
     return false;
 }
 template <typename T, typename Tk, typename... Args>
 static inline bool SetHasKeys(const std::set<T> &set, const Tk &key,
                               const Args &... args) {
     return (set.count(key) != 0) || SetHasKeys(set, args...);
 }
 
 // outpoint (needed for the utxo index) + nHeight + fCoinBase
 static constexpr size_t PER_UTXO_OVERHEAD =
     sizeof(COutPoint) + sizeof(uint32_t) + sizeof(bool);
 
 static UniValue getblockstats(const Config &config,
                               const JSONRPCRequest &request) {
     if (request.fHelp || request.params.size() < 1 ||
         request.params.size() > 4) {
         throw std::runtime_error(RPCHelpMan{
             "getblockstats",
             "\nCompute per block statistics for a given window. All "
             "amounts are in " +
                 CURRENCY_UNIT +
                 ".\n"
                 "It won't work for some heights with pruning.\n"
                 "It won't work without -txindex for utxo_size_inc, *fee or "
                 "*feerate stats.\n",
             {
                 {"hash_or_height",
                  RPCArg::Type::NUM,
-                 /* opt */ false,
-                 /* default_val */ "",
+                 RPCArg::Optional::NO,
                  "The block hash or height of the target block",
                  "",
                  {"", "string or numeric"}},
                 {"stats",
                  RPCArg::Type::ARR,
-                 /* opt */ true,
-                 /* default_val */ "all values",
+                 /* default */ "all values",
                  "Values to plot (see result below)",
                  {
-                     {"height", RPCArg::Type::STR, /* opt */ true,
-                      /* default_val */ "", "Selected statistic"},
-                     {"time", RPCArg::Type::STR, /* opt */ true,
-                      /* default_val */ "", "Selected statistic"},
+                     {"height", RPCArg::Type::STR, RPCArg::Optional::OMITTED,
+                      "Selected statistic"},
+                     {"time", RPCArg::Type::STR, RPCArg::Optional::OMITTED,
+                      "Selected statistic"},
                  },
                  "stats"},
             },
             RPCResult{
                 "{                           (json object)\n"
                 "  \"avgfee\": x.xxx,          (numeric) Average fee in the "
                 "block\n"
                 "  \"avgfeerate\": x.xxx,      (numeric) Average feerate (in " +
                 CURRENCY_UNIT +
                 " per byte)\n"
                 "  \"avgtxsize\": xxxxx,       (numeric) Average transaction "
                 "size\n"
                 "  \"blockhash\": xxxxx,       (string) The block hash (to "
                 "check for potential reorgs)\n"
                 "  \"height\": xxxxx,          (numeric) The height of the "
                 "block\n"
                 "  \"ins\": xxxxx,             (numeric) The number of inputs "
                 "(excluding coinbase)\n"
                 "  \"maxfee\": xxxxx,          (numeric) Maximum fee in the "
                 "block\n"
                 "  \"maxfeerate\": xxxxx,      (numeric) Maximum feerate (in " +
                 CURRENCY_UNIT +
                 " per byte)\n"
                 "  \"maxtxsize\": xxxxx,       (numeric) Maximum transaction "
                 "size\n"
                 "  \"medianfee\": x.xxx,       (numeric) Truncated median fee "
                 "in the block\n"
                 "  \"medianfeerate\": x.xxx,   (numeric) Truncated median "
                 "feerate (in " +
                 CURRENCY_UNIT +
                 " per byte)\n"
                 "  \"mediantime\": xxxxx,      (numeric) The block median time "
                 "past\n"
                 "  \"mediantxsize\": xxxxx,    (numeric) Truncated median "
                 "transaction size\n"
                 "  \"minfee\": x.xxx,          (numeric) Minimum fee in the "
                 "block\n"
                 "  \"minfeerate\": xx.xx,      (numeric) Minimum feerate (in " +
                 CURRENCY_UNIT +
                 " per byte)\n"
                 "  \"mintxsize\": xxxxx,       (numeric) Minimum transaction "
                 "size\n"
                 "  \"outs\": xxxxx,            (numeric) The number of "
                 "outputs\n"
                 "  \"subsidy\": x.xxx,         (numeric) The block subsidy\n"
                 "  \"time\": xxxxx,            (numeric) The block time\n"
                 "  \"total_out\": x.xxx,       (numeric) Total amount in all "
                 "outputs (excluding coinbase and thus reward [ie subsidy + "
                 "totalfee])\n"
                 "  \"total_size\": xxxxx,      (numeric) Total size of all "
                 "non-coinbase transactions\n"
                 "  \"totalfee\": x.xxx,        (numeric) The fee total\n"
                 "  \"txs\": xxxxx,             (numeric) The number of "
                 "transactions (excluding coinbase)\n"
                 "  \"utxo_increase\": xxxxx,   (numeric) The increase/decrease "
                 "in the number of unspent outputs\n"
                 "  \"utxo_size_inc\": xxxxx,   (numeric) The increase/decrease "
                 "in size for the utxo index (not discounting op_return and "
                 "similar)\n"
                 "}\n"},
             RPCExamples{
                 HelpExampleCli("getblockstats",
                                "1000 '[\"minfeerate\",\"avgfeerate\"]'") +
                 HelpExampleRpc("getblockstats",
                                "1000 '[\"minfeerate\",\"avgfeerate\"]'")},
         }
                                      .ToString());
     }
 
     LOCK(cs_main);
 
     CBlockIndex *pindex;
     if (request.params[0].isNum()) {
         const int height = request.params[0].get_int();
         const int current_tip = ::ChainActive().Height();
         if (height < 0) {
             throw JSONRPCError(
                 RPC_INVALID_PARAMETER,
                 strprintf("Target block height %d is negative", height));
         }
         if (height > current_tip) {
             throw JSONRPCError(
                 RPC_INVALID_PARAMETER,
                 strprintf("Target block height %d after current tip %d", height,
                           current_tip));
         }
 
         pindex = ::ChainActive()[height];
     } else {
         const BlockHash hash(ParseHashV(request.params[0], "hash_or_height"));
         pindex = LookupBlockIndex(hash);
         if (!pindex) {
             throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Block not found");
         }
         if (!::ChainActive().Contains(pindex)) {
             throw JSONRPCError(RPC_INVALID_PARAMETER,
                                strprintf("Block is not in chain %s",
                                          Params().NetworkIDString()));
         }
     }
 
     assert(pindex != nullptr);
 
     std::set<std::string> stats;
     if (!request.params[1].isNull()) {
         const UniValue stats_univalue = request.params[1].get_array();
         for (unsigned int i = 0; i < stats_univalue.size(); i++) {
             const std::string stat = stats_univalue[i].get_str();
             stats.insert(stat);
         }
     }
 
     const CBlock block = GetBlockChecked(config, pindex);
 
     // Calculate everything if nothing selected (default)
     const bool do_all = stats.size() == 0;
     const bool do_mediantxsize = do_all || stats.count("mediantxsize") != 0;
     const bool do_medianfee = do_all || stats.count("medianfee") != 0;
     const bool do_medianfeerate = do_all || stats.count("medianfeerate") != 0;
     const bool loop_inputs =
         do_all || do_medianfee || do_medianfeerate ||
         SetHasKeys(stats, "utxo_size_inc", "totalfee", "avgfee", "avgfeerate",
                    "minfee", "maxfee", "minfeerate", "maxfeerate");
     const bool loop_outputs = do_all || loop_inputs || stats.count("total_out");
     const bool do_calculate_size =
         do_mediantxsize || loop_inputs ||
         SetHasKeys(stats, "total_size", "avgtxsize", "mintxsize", "maxtxsize");
 
     const int64_t blockMaxSize = config.GetMaxBlockSize();
     Amount maxfee = Amount::zero();
     Amount maxfeerate = Amount::zero();
     Amount minfee = MAX_MONEY;
     Amount minfeerate = MAX_MONEY;
     Amount total_out = Amount::zero();
     Amount totalfee = Amount::zero();
     int64_t inputs = 0;
     int64_t maxtxsize = 0;
     int64_t mintxsize = blockMaxSize;
     int64_t outputs = 0;
     int64_t total_size = 0;
     int64_t utxo_size_inc = 0;
     std::vector<Amount> fee_array;
     std::vector<Amount> feerate_array;
     std::vector<int64_t> txsize_array;
 
     const Consensus::Params &params = config.GetChainParams().GetConsensus();
 
     for (const auto &tx : block.vtx) {
         outputs += tx->vout.size();
         Amount tx_total_out = Amount::zero();
         if (loop_outputs) {
             for (const CTxOut &out : tx->vout) {
                 tx_total_out += out.nValue;
                 utxo_size_inc +=
                     GetSerializeSize(out, PROTOCOL_VERSION) + PER_UTXO_OVERHEAD;
             }
         }
 
         if (tx->IsCoinBase()) {
             continue;
         }
 
         // Don't count coinbase's fake input
         inputs += tx->vin.size();
         // Don't count coinbase reward
         total_out += tx_total_out;
 
         int64_t tx_size = 0;
         if (do_calculate_size) {
             tx_size = tx->GetTotalSize();
             if (do_mediantxsize) {
                 txsize_array.push_back(tx_size);
             }
             maxtxsize = std::max(maxtxsize, tx_size);
             mintxsize = std::min(mintxsize, tx_size);
             total_size += tx_size;
         }
 
         if (loop_inputs) {
             if (!g_txindex) {
                 throw JSONRPCError(RPC_INVALID_PARAMETER,
                                    "One or more of the selected stats requires "
                                    "-txindex enabled");
             }
 
             Amount tx_total_in = Amount::zero();
             for (const CTxIn &in : tx->vin) {
                 CTransactionRef tx_in;
                 BlockHash hashBlock;
                 if (!GetTransaction(in.prevout.GetTxId(), tx_in, params,
                                     hashBlock)) {
                     throw JSONRPCError(RPC_INTERNAL_ERROR,
                                        std::string("Unexpected internal error "
                                                    "(tx index seems corrupt)"));
                 }
 
                 CTxOut prevoutput = tx_in->vout[in.prevout.GetN()];
 
                 tx_total_in += prevoutput.nValue;
                 utxo_size_inc -=
                     GetSerializeSize(prevoutput, PROTOCOL_VERSION) +
                     PER_UTXO_OVERHEAD;
             }
 
             Amount txfee = tx_total_in - tx_total_out;
             assert(MoneyRange(txfee));
             if (do_medianfee) {
                 fee_array.push_back(txfee);
             }
             maxfee = std::max(maxfee, txfee);
             minfee = std::min(minfee, txfee);
             totalfee += txfee;
 
             Amount feerate = txfee / tx_size;
             if (do_medianfeerate) {
                 feerate_array.push_back(feerate);
             }
             maxfeerate = std::max(maxfeerate, feerate);
             minfeerate = std::min(minfeerate, feerate);
         }
     }
 
     UniValue ret_all(UniValue::VOBJ);
     ret_all.pushKV("avgfee",
                    ValueFromAmount((block.vtx.size() > 1)
                                        ? totalfee / int((block.vtx.size() - 1))
                                        : Amount::zero()));
     ret_all.pushKV("avgfeerate",
                    ValueFromAmount((total_size > 0) ? totalfee / total_size
                                                     : Amount::zero()));
     ret_all.pushKV("avgtxsize", (block.vtx.size() > 1)
                                     ? total_size / (block.vtx.size() - 1)
                                     : 0);
     ret_all.pushKV("blockhash", pindex->GetBlockHash().GetHex());
     ret_all.pushKV("height", (int64_t)pindex->nHeight);
     ret_all.pushKV("ins", inputs);
     ret_all.pushKV("maxfee", ValueFromAmount(maxfee));
     ret_all.pushKV("maxfeerate", ValueFromAmount(maxfeerate));
     ret_all.pushKV("maxtxsize", maxtxsize);
     ret_all.pushKV("medianfee",
                    ValueFromAmount(CalculateTruncatedMedian(fee_array)));
     ret_all.pushKV("medianfeerate",
                    ValueFromAmount(CalculateTruncatedMedian(feerate_array)));
     ret_all.pushKV("mediantime", pindex->GetMedianTimePast());
     ret_all.pushKV("mediantxsize", CalculateTruncatedMedian(txsize_array));
     ret_all.pushKV(
         "minfee",
         ValueFromAmount((minfee == MAX_MONEY) ? Amount::zero() : minfee));
     ret_all.pushKV("minfeerate",
                    ValueFromAmount((minfeerate == MAX_MONEY) ? Amount::zero()
                                                              : minfeerate));
     ret_all.pushKV("mintxsize", mintxsize == blockMaxSize ? 0 : mintxsize);
     ret_all.pushKV("outs", outputs);
     ret_all.pushKV("subsidy", ValueFromAmount(GetBlockSubsidy(
                                   pindex->nHeight, Params().GetConsensus())));
     ret_all.pushKV("time", pindex->GetBlockTime());
     ret_all.pushKV("total_out", ValueFromAmount(total_out));
     ret_all.pushKV("total_size", total_size);
     ret_all.pushKV("totalfee", ValueFromAmount(totalfee));
     ret_all.pushKV("txs", (int64_t)block.vtx.size());
     ret_all.pushKV("utxo_increase", outputs - inputs);
     ret_all.pushKV("utxo_size_inc", utxo_size_inc);
 
     if (do_all) {
         return ret_all;
     }
 
     UniValue ret(UniValue::VOBJ);
     for (const std::string &stat : stats) {
         const UniValue &value = ret_all[stat];
         if (value.isNull()) {
             throw JSONRPCError(
                 RPC_INVALID_PARAMETER,
                 strprintf("Invalid selected statistic %s", stat));
         }
         ret.pushKV(stat, value);
     }
     return ret;
 }
 
 static UniValue savemempool(const Config &config,
                             const JSONRPCRequest &request) {
     if (request.fHelp || request.params.size() != 0) {
         throw std::runtime_error(RPCHelpMan{
             "savemempool",
             "\nDumps the mempool to disk. It will fail until the "
             "previous dump is fully loaded.\n",
             {},
             RPCResults{},
             RPCExamples{HelpExampleCli("savemempool", "") +
                         HelpExampleRpc("savemempool", "")},
         }
                                      .ToString());
     }
 
     if (!::g_mempool.IsLoaded()) {
         throw JSONRPCError(RPC_MISC_ERROR, "The mempool was not loaded yet");
     }
 
     if (!DumpMempool(::g_mempool)) {
         throw JSONRPCError(RPC_MISC_ERROR, "Unable to dump mempool to disk");
     }
 
     return NullUniValue;
 }
 
 //! Search for a given set of pubkey scripts
 static bool FindScriptPubKey(std::atomic<int> &scan_progress,
                              const std::atomic<bool> &should_abort,
                              int64_t &count, CCoinsViewCursor *cursor,
                              const std::set<CScript> &needles,
                              std::map<COutPoint, Coin> &out_results) {
     scan_progress = 0;
     count = 0;
     while (cursor->Valid()) {
         COutPoint key;
         Coin coin;
         if (!cursor->GetKey(key) || !cursor->GetValue(coin)) {
             return false;
         }
         if (++count % 8192 == 0) {
             boost::this_thread::interruption_point();
             if (should_abort) {
                 // allow to abort the scan via the abort reference
                 return false;
             }
         }
         if (count % 256 == 0) {
             // update progress reference every 256 item
             const TxId &txid = key.GetTxId();
             uint32_t high = 0x100 * *txid.begin() + *(txid.begin() + 1);
             scan_progress = int(high * 100.0 / 65536.0 + 0.5);
         }
         if (needles.count(coin.GetTxOut().scriptPubKey)) {
             out_results.emplace(key, coin);
         }
         cursor->Next();
     }
     scan_progress = 100;
     return true;
 }
 
 /** RAII object to prevent concurrency issue when scanning the txout set */
 static std::mutex g_utxosetscan;
 static std::atomic<int> g_scan_progress;
 static std::atomic<bool> g_scan_in_progress;
 static std::atomic<bool> g_should_abort_scan;
 class CoinsViewScanReserver {
 private:
     bool m_could_reserve;
 
 public:
     explicit CoinsViewScanReserver() : m_could_reserve(false) {}
 
     bool reserve() {
         assert(!m_could_reserve);
         std::lock_guard<std::mutex> lock(g_utxosetscan);
         if (g_scan_in_progress) {
             return false;
         }
         g_scan_in_progress = true;
         m_could_reserve = true;
         return true;
     }
 
     ~CoinsViewScanReserver() {
         if (m_could_reserve) {
             std::lock_guard<std::mutex> lock(g_utxosetscan);
             g_scan_in_progress = false;
         }
     }
 };
 
 static UniValue scantxoutset(const Config &config,
                              const JSONRPCRequest &request) {
     if (request.fHelp || request.params.size() < 1 ||
         request.params.size() > 2) {
         throw std::runtime_error(RPCHelpMan{
             "scantxoutset",
             "\nEXPERIMENTAL warning: this call may be removed or changed "
             "in future releases.\n"
             "\nScans the unspent transaction output set for entries that "
             "match certain output descriptors.\n"
             "Examples of output descriptors are:\n"
             "    addr(<address>)                      Outputs whose "
             "scriptPubKey corresponds to the specified address (does not "
             "include P2PK)\n"
             "    raw(<hex script>)                    Outputs whose "
             "scriptPubKey equals the specified hex scripts\n"
             "    combo(<pubkey>)                      P2PK and P2PKH "
             "outputs for the given pubkey\n"
             "    pkh(<pubkey>)                        P2PKH outputs for "
             "the given pubkey\n"
             "    sh(multi(<n>,<pubkey>,<pubkey>,...)) P2SH-multisig "
             "outputs for the given threshold and pubkeys\n"
             "\nIn the above, <pubkey> either refers to a fixed public key "
             "in hexadecimal notation, or to an xpub/xprv optionally "
             "followed by one\n"
             "or more path elements separated by \"/\", and optionally "
             "ending in \"/*\" (unhardened), or \"/*'\" or \"/*h\" "
             "(hardened) to specify all\n"
             "unhardened or hardened child keys.\n"
             "In the latter case, a range needs to be specified by below if "
             "different from 1000.\n"
             "For more information on output descriptors, see the "
             "documentation in the doc/descriptors.md file.\n",
             {
-                {"action", RPCArg::Type::STR, /* opt */ false,
-                 /* default_val */ "",
+                {"action", RPCArg::Type::STR, RPCArg::Optional::NO,
                  "The action to execute\n"
                  "                                      \"start\" for "
                  "starting a scan\n"
                  "                                      \"abort\" for "
                  "aborting the current scan (returns true when abort was "
                  "successful)\n"
                  "                                      \"status\" for "
                  "progress report (in %) of the current scan"},
                 {"scanobjects",
                  RPCArg::Type::ARR,
-                 /* opt */ false,
-                 /* default_val */ "",
+                 RPCArg::Optional::NO,
                  "Array of scan objects\n"
                  "                                  Every scan object is "
                  "either a string descriptor or an object:",
                  {
-                     {"descriptor", RPCArg::Type::STR, /* opt */ true,
-                      /* default_val */ "", "An output descriptor"},
+                     {"descriptor", RPCArg::Type::STR,
+                      RPCArg::Optional::OMITTED, "An output descriptor"},
                      {
                          "",
                          RPCArg::Type::OBJ,
-                         /* opt */ true,
-                         /* default_val */ "",
+                         RPCArg::Optional::OMITTED,
                          "An object with output descriptor and metadata",
                          {
-                             {"desc", RPCArg::Type::STR, /* opt */ false,
-                              /* default_val */ "", "An output descriptor"},
-                             {"range", RPCArg::Type::NUM, /* opt */ true,
-                              /* default_val */ "1000",
+                             {"desc", RPCArg::Type::STR, RPCArg::Optional::NO,
+                              "An output descriptor"},
+                             {"range", RPCArg::Type::NUM, /* default */ "1000",
                               "Up to what child index HD chains should be "
                               "explored"},
                          },
                      },
                  },
                  "[scanobjects,...]"},
             },
             RPCResult{
                 "{\n"
                 "  \"unspents\": [\n"
                 "    {\n"
                 "    \"txid\" : \"transactionid\",     (string) The "
                 "transaction id\n"
                 "    \"vout\": n,                    (numeric) the vout value\n"
                 "    \"scriptPubKey\" : \"script\",    (string) the script "
                 "key\n"
                 "    \"desc\" : \"descriptor\",        (string) A specialized "
                 "descriptor for the matched scriptPubKey\n"
                 "    \"amount\" : x.xxx,             (numeric) The total "
                 "amount in " +
                 CURRENCY_UNIT +
                 " of the unspent output\n"
                 "    \"height\" : n,                 (numeric) Height of the "
                 "unspent transaction output\n"
                 "   }\n"
                 "   ,...], \n"
                 " \"total_amount\" : x.xxx,          (numeric) The total "
                 "amount of all found unspent outputs in " +
                 CURRENCY_UNIT +
                 "\n"
                 "]\n"},
             RPCExamples{""},
         }
                                      .ToString());
     }
 
     RPCTypeCheck(request.params, {UniValue::VSTR, UniValue::VARR});
 
     UniValue result(UniValue::VOBJ);
     if (request.params[0].get_str() == "status") {
         CoinsViewScanReserver reserver;
         if (reserver.reserve()) {
             // no scan in progress
             return NullUniValue;
         }
         result.pushKV("progress", g_scan_progress.load());
         return result;
     } else if (request.params[0].get_str() == "abort") {
         CoinsViewScanReserver reserver;
         if (reserver.reserve()) {
             // reserve was possible which means no scan was running
             return false;
         }
         // set the abort flag
         g_should_abort_scan = true;
         return true;
     } else if (request.params[0].get_str() == "start") {
         CoinsViewScanReserver reserver;
         if (!reserver.reserve()) {
             throw JSONRPCError(
                 RPC_INVALID_PARAMETER,
                 "Scan already in progress, use action \"abort\" or \"status\"");
         }
         std::set<CScript> needles;
         std::map<CScript, std::string> descriptors;
         Amount total_in = Amount::zero();
 
         // loop through the scan objects
         for (const UniValue &scanobject :
              request.params[1].get_array().getValues()) {
             std::string desc_str;
             int range = 1000;
             if (scanobject.isStr()) {
                 desc_str = scanobject.get_str();
             } else if (scanobject.isObject()) {
                 UniValue desc_uni = find_value(scanobject, "desc");
                 if (desc_uni.isNull()) {
                     throw JSONRPCError(
                         RPC_INVALID_PARAMETER,
                         "Descriptor needs to be provided in scan object");
                 }
                 desc_str = desc_uni.get_str();
                 UniValue range_uni = find_value(scanobject, "range");
                 if (!range_uni.isNull()) {
                     range = range_uni.get_int();
                     if (range < 0 || range > 1000000) {
                         throw JSONRPCError(RPC_INVALID_PARAMETER,
                                            "range out of range");
                     }
                 }
             } else {
                 throw JSONRPCError(
                     RPC_INVALID_PARAMETER,
                     "Scan object needs to be either a string or an object");
             }
 
             FlatSigningProvider provider;
             auto desc = Parse(desc_str, provider);
             if (!desc) {
                 throw JSONRPCError(
                     RPC_INVALID_ADDRESS_OR_KEY,
                     strprintf("Invalid descriptor '%s'", desc_str));
             }
             if (!desc->IsRange()) {
                 range = 0;
             }
             for (int i = 0; i <= range; ++i) {
                 std::vector<CScript> scripts;
                 if (!desc->Expand(i, provider, scripts, provider)) {
                     throw JSONRPCError(
                         RPC_INVALID_ADDRESS_OR_KEY,
                         strprintf(
                             "Cannot derive script without private keys: '%s'",
                             desc_str));
                 }
                 for (const auto &script : scripts) {
                     std::string inferred =
                         InferDescriptor(script, provider)->ToString();
                     needles.emplace(script);
                     descriptors.emplace(std::move(script), std::move(inferred));
                 }
             }
         }
 
         // Scan the unspent transaction output set for inputs
         UniValue unspents(UniValue::VARR);
         std::vector<CTxOut> input_txos;
         std::map<COutPoint, Coin> coins;
         g_should_abort_scan = false;
         g_scan_progress = 0;
         int64_t count = 0;
         std::unique_ptr<CCoinsViewCursor> pcursor;
         {
             LOCK(cs_main);
             ::ChainstateActive().ForceFlushStateToDisk();
             pcursor = std::unique_ptr<CCoinsViewCursor>(pcoinsdbview->Cursor());
             assert(pcursor);
         }
         bool res = FindScriptPubKey(g_scan_progress, g_should_abort_scan, count,
                                     pcursor.get(), needles, coins);
         result.pushKV("success", res);
         result.pushKV("searched_items", count);
 
         for (const auto &it : coins) {
             const COutPoint &outpoint = it.first;
             const Coin &coin = it.second;
             const CTxOut &txo = coin.GetTxOut();
             input_txos.push_back(txo);
             total_in += txo.nValue;
 
             UniValue unspent(UniValue::VOBJ);
             unspent.pushKV("txid", outpoint.GetTxId().GetHex());
             unspent.pushKV("vout", int32_t(outpoint.GetN()));
             unspent.pushKV("scriptPubKey", HexStr(txo.scriptPubKey.begin(),
                                                   txo.scriptPubKey.end()));
             unspent.pushKV("desc", descriptors[txo.scriptPubKey]);
             unspent.pushKV("amount", ValueFromAmount(txo.nValue));
             unspent.pushKV("height", int32_t(coin.GetHeight()));
 
             unspents.push_back(unspent);
         }
         result.pushKV("unspents", unspents);
         result.pushKV("total_amount", ValueFromAmount(total_in));
     } else {
         throw JSONRPCError(RPC_INVALID_PARAMETER, "Invalid command");
     }
     return result;
 }
 
 // clang-format off
 static const CRPCCommand commands[] = {
     //  category            name                      actor (function)        argNames
     //  ------------------- ------------------------  ----------------------  ----------
     { "blockchain",         "getbestblockhash",       getbestblockhash,       {} },
     { "blockchain",         "getblock",               getblock,               {"blockhash","verbosity|verbose"} },
     { "blockchain",         "getblockchaininfo",      getblockchaininfo,      {} },
     { "blockchain",         "getblockcount",          getblockcount,          {} },
     { "blockchain",         "getblockhash",           getblockhash,           {"height"} },
     { "blockchain",         "getblockheader",         getblockheader,         {"blockhash","verbose"} },
     { "blockchain",         "getblockstats",          getblockstats,          {"hash_or_height","stats"} },
     { "blockchain",         "getchaintips",           getchaintips,           {} },
     { "blockchain",         "getchaintxstats",        getchaintxstats,        {"nblocks", "blockhash"} },
     { "blockchain",         "getdifficulty",          getdifficulty,          {} },
     { "blockchain",         "getmempoolancestors",    getmempoolancestors,    {"txid","verbose"} },
     { "blockchain",         "getmempooldescendants",  getmempooldescendants,  {"txid","verbose"} },
     { "blockchain",         "getmempoolentry",        getmempoolentry,        {"txid"} },
     { "blockchain",         "getmempoolinfo",         getmempoolinfo,         {} },
     { "blockchain",         "getrawmempool",          getrawmempool,          {"verbose"} },
     { "blockchain",         "gettxout",               gettxout,               {"txid","n","include_mempool"} },
     { "blockchain",         "gettxoutsetinfo",        gettxoutsetinfo,        {} },
     { "blockchain",         "pruneblockchain",        pruneblockchain,        {"height"} },
     { "blockchain",         "savemempool",            savemempool,            {} },
     { "blockchain",         "verifychain",            verifychain,            {"checklevel","nblocks"} },
     { "blockchain",         "preciousblock",          preciousblock,          {"blockhash"} },
     { "blockchain",         "scantxoutset",           scantxoutset,           {"action", "scanobjects"} },
 
     /* Not shown in help */
     { "hidden",             "getfinalizedblockhash",            getfinalizedblockhash,            {} },
     { "hidden",             "finalizeblock",                    finalizeblock,                    {"blockhash"} },
     { "hidden",             "invalidateblock",                  invalidateblock,                  {"blockhash"} },
     { "hidden",             "parkblock",                        parkblock,                        {"blockhash"} },
     { "hidden",             "reconsiderblock",                  reconsiderblock,                  {"blockhash"} },
     { "hidden",             "syncwithvalidationinterfacequeue", syncwithvalidationinterfacequeue, {} },
     { "hidden",             "unparkblock",                      unparkblock,                      {"blockhash"} },
     { "hidden",             "waitfornewblock",                  waitfornewblock,                  {"timeout"} },
     { "hidden",             "waitforblock",                     waitforblock,                     {"blockhash","timeout"} },
     { "hidden",             "waitforblockheight",               waitforblockheight,               {"height","timeout"} },
 };
 // clang-format on
 
 void RegisterBlockchainRPCCommands(CRPCTable &t) {
     for (unsigned int vcidx = 0; vcidx < ARRAYLEN(commands); vcidx++) {
         t.appendCommand(commands[vcidx].name, &commands[vcidx]);
     }
 }
diff --git a/src/rpc/mining.cpp b/src/rpc/mining.cpp
index 5647b5326..91b28e4ed 100644
--- a/src/rpc/mining.cpp
+++ b/src/rpc/mining.cpp
@@ -1,901 +1,894 @@
 // Copyright (c) 2010 Satoshi Nakamoto
 // Copyright (c) 2009-2018 The Bitcoin Core developers
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
 #include <amount.h>
 #include <blockvalidity.h>
 #include <chain.h>
 #include <chainparams.h>
 #include <config.h>
 #include <consensus/consensus.h>
 #include <consensus/params.h>
 #include <consensus/validation.h>
 #include <core_io.h>
 #include <key_io.h>
 #include <miner.h>
 #include <net.h>
 #include <policy/policy.h>
 #include <pow.h>
 #include <rpc/blockchain.h>
 #include <rpc/mining.h>
 #include <rpc/server.h>
 #include <rpc/util.h>
 #include <shutdown.h>
 #include <txmempool.h>
 #include <util/strencodings.h>
 #include <util/system.h>
 #include <util/validation.h>
 #include <validation.h>
 #include <validationinterface.h>
 #include <warnings.h>
 
 #include <univalue.h>
 
 #include <cstdint>
 #include <memory>
 
 /**
  * Return average network hashes per second based on the last 'lookup' blocks,
  * or from the last difficulty change if 'lookup' is nonpositive. If 'height' is
  * nonnegative, compute the estimate at the time when a given block was found.
  */
 static UniValue GetNetworkHashPS(int lookup, int height) {
     CBlockIndex *pb = ::ChainActive().Tip();
 
     if (height >= 0 && height < ::ChainActive().Height()) {
         pb = ::ChainActive()[height];
     }
 
     if (pb == nullptr || !pb->nHeight) {
         return 0;
     }
 
     // If lookup is -1, then use blocks since last difficulty change.
     if (lookup <= 0) {
         lookup = pb->nHeight %
                      Params().GetConsensus().DifficultyAdjustmentInterval() +
                  1;
     }
 
     // If lookup is larger than chain, then set it to chain length.
     if (lookup > pb->nHeight) {
         lookup = pb->nHeight;
     }
 
     CBlockIndex *pb0 = pb;
     int64_t minTime = pb0->GetBlockTime();
     int64_t maxTime = minTime;
     for (int i = 0; i < lookup; i++) {
         pb0 = pb0->pprev;
         int64_t time = pb0->GetBlockTime();
         minTime = std::min(time, minTime);
         maxTime = std::max(time, maxTime);
     }
 
     // In case there's a situation where minTime == maxTime, we don't want a
     // divide by zero exception.
     if (minTime == maxTime) {
         return 0;
     }
 
     arith_uint256 workDiff = pb->nChainWork - pb0->nChainWork;
     int64_t timeDiff = maxTime - minTime;
 
     return workDiff.getdouble() / timeDiff;
 }
 
 static UniValue getnetworkhashps(const Config &config,
                                  const JSONRPCRequest &request) {
     if (request.fHelp || request.params.size() > 2) {
         throw std::runtime_error(RPCHelpMan{
             "getnetworkhashps",
             "\nReturns the estimated network hashes per second "
             "based on the last n blocks.\n"
             "Pass in [blocks] to override # of blocks, -1 specifies "
             "since last difficulty change.\n"
             "Pass in [height] to estimate the network speed at the "
             "time when a certain block was found.\n",
             {
-                {"nblocks", RPCArg::Type::NUM, /* opt */ true,
-                 /* default_val */ "120",
+                {"nblocks", RPCArg::Type::NUM, /* default */ "120",
                  "The number of blocks, or -1 for blocks since last "
                  "difficulty change."},
-                {"height", RPCArg::Type::NUM, /* opt */ true,
-                 /* default_val */ "-1",
+                {"height", RPCArg::Type::NUM, /* default */ "-1",
                  "To estimate at the time of the given height."},
             },
             RPCResult{"x             (numeric) Hashes per second estimated\n"},
             RPCExamples{HelpExampleCli("getnetworkhashps", "") +
                         HelpExampleRpc("getnetworkhashps", "")},
         }
                                      .ToString());
     }
 
     LOCK(cs_main);
     return GetNetworkHashPS(
         !request.params[0].isNull() ? request.params[0].get_int() : 120,
         !request.params[1].isNull() ? request.params[1].get_int() : -1);
 }
 
 UniValue generateBlocks(const Config &config,
                         std::shared_ptr<CReserveScript> coinbaseScript,
                         int nGenerate, uint64_t nMaxTries, bool keepScript) {
     static const int nInnerLoopCount = 0x100000;
     int nHeightEnd = 0;
     int nHeight = 0;
 
     {
         // Don't keep cs_main locked.
         LOCK(cs_main);
         nHeight = ::ChainActive().Height();
         nHeightEnd = nHeight + nGenerate;
     }
 
     const uint64_t nExcessiveBlockSize = config.GetMaxBlockSize();
 
     unsigned int nExtraNonce = 0;
     UniValue blockHashes(UniValue::VARR);
     while (nHeight < nHeightEnd && !ShutdownRequested()) {
         std::unique_ptr<CBlockTemplate> pblocktemplate(
             BlockAssembler(config, g_mempool)
                 .CreateNewBlock(coinbaseScript->reserveScript));
 
         if (!pblocktemplate.get()) {
             throw JSONRPCError(RPC_INTERNAL_ERROR, "Couldn't create new block");
         }
 
         CBlock *pblock = &pblocktemplate->block;
 
         {
             LOCK(cs_main);
             IncrementExtraNonce(pblock, ::ChainActive().Tip(),
                                 nExcessiveBlockSize, nExtraNonce);
         }
 
         while (nMaxTries > 0 && pblock->nNonce < nInnerLoopCount &&
                !CheckProofOfWork(pblock->GetHash(), pblock->nBits,
                                  config.GetChainParams().GetConsensus())) {
             ++pblock->nNonce;
             --nMaxTries;
         }
 
         if (nMaxTries == 0) {
             break;
         }
 
         if (pblock->nNonce == nInnerLoopCount) {
             continue;
         }
 
         std::shared_ptr<const CBlock> shared_pblock =
             std::make_shared<const CBlock>(*pblock);
         if (!ProcessNewBlock(config, shared_pblock, true, nullptr)) {
             throw JSONRPCError(RPC_INTERNAL_ERROR,
                                "ProcessNewBlock, block not accepted");
         }
         ++nHeight;
         blockHashes.push_back(pblock->GetHash().GetHex());
 
         // Mark script as important because it was used at least for one
         // coinbase output if the script came from the wallet.
         if (keepScript) {
             coinbaseScript->KeepScript();
         }
     }
 
     return blockHashes;
 }
 
 static UniValue generatetoaddress(const Config &config,
                                   const JSONRPCRequest &request) {
     if (request.fHelp || request.params.size() < 2 ||
         request.params.size() > 3) {
         throw std::runtime_error(RPCHelpMan{
             "generatetoaddress",
             "\nMine blocks immediately to a specified address before the "
             "RPC call returns)\n",
             {
-                {"nblocks", RPCArg::Type::NUM, /* opt */ false,
-                 /* default_val */ "",
+                {"nblocks", RPCArg::Type::NUM, RPCArg::Optional::NO,
                  "How many blocks are generated immediately."},
-                {"address", RPCArg::Type::STR, /* opt */ false,
-                 /* default_val */ "",
+                {"address", RPCArg::Type::STR, RPCArg::Optional::NO,
                  "The address to send the newly generated bitcoin to."},
-                {"maxtries", RPCArg::Type::NUM, /* opt */ true,
-                 /* default_val */ "1000000", "How many iterations to try."},
+                {"maxtries", RPCArg::Type::NUM, /* default */ "1000000",
+                 "How many iterations to try."},
             },
             RPCResult{
                 "[ blockhashes ]     (array) hashes of blocks generated\n"},
             RPCExamples{
                 "\nGenerate 11 blocks to myaddress\n" +
                 HelpExampleCli("generatetoaddress", "11 \"myaddress\"") +
                 "If you are running the bitcoin core wallet, you can get a new "
                 "address to send the newly generated bitcoin to with:\n" +
                 HelpExampleCli("getnewaddress", "")},
         }
                                      .ToString());
     }
 
     int nGenerate = request.params[0].get_int();
     uint64_t nMaxTries = 1000000;
     if (!request.params[2].isNull()) {
         nMaxTries = request.params[2].get_int();
     }
 
     CTxDestination destination =
         DecodeDestination(request.params[1].get_str(), config.GetChainParams());
     if (!IsValidDestination(destination)) {
         throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY,
                            "Error: Invalid address");
     }
 
     std::shared_ptr<CReserveScript> coinbaseScript =
         std::make_shared<CReserveScript>();
     coinbaseScript->reserveScript = GetScriptForDestination(destination);
 
     return generateBlocks(config, coinbaseScript, nGenerate, nMaxTries, false);
 }
 
 static UniValue getmininginfo(const Config &config,
                               const JSONRPCRequest &request) {
     if (request.fHelp || request.params.size() != 0) {
         throw std::runtime_error(RPCHelpMan{
             "getmininginfo",
             "\nReturns a json object containing mining-related "
             "information.",
             {},
             RPCResult{
                 "{\n"
                 "  \"blocks\": nnn,             (numeric) The current block\n"
                 "  \"currentblocksize\": nnn,   (numeric, optional) The block "
                 "size of the last assembled block (only present if a block was "
                 "ever assembled)\n"
                 "  \"currentblocktx\": nnn,     (numeric, optional) The number "
                 "of block transactions of the last assembled block (only "
                 "present if a block was ever assembled)\n"
                 "  \"difficulty\": xxx.xxxxx    (numeric) The current "
                 "difficulty\n"
                 "  \"networkhashps\": nnn,      (numeric) The network hashes "
                 "per second\n"
                 "  \"pooledtx\": n              (numeric) The size of the "
                 "mempool\n"
                 "  \"chain\": \"xxxx\",           (string) current network "
                 "name as defined in BIP70 (main, test, regtest)\n"
                 "  \"warnings\": \"...\"          (string) any network and "
                 "blockchain warnings\n"
                 "}\n"},
             RPCExamples{HelpExampleCli("getmininginfo", "") +
                         HelpExampleRpc("getmininginfo", "")},
         }
                                      .ToString());
     }
 
     LOCK(cs_main);
 
     UniValue obj(UniValue::VOBJ);
     obj.pushKV("blocks", int(::ChainActive().Height()));
     if (BlockAssembler::m_last_block_size) {
         obj.pushKV("currentblocksize", *BlockAssembler::m_last_block_size);
     }
     if (BlockAssembler::m_last_block_num_txs) {
         obj.pushKV("currentblocktx", *BlockAssembler::m_last_block_num_txs);
     }
     obj.pushKV("difficulty", double(GetDifficulty(::ChainActive().Tip())));
     obj.pushKV("networkhashps", getnetworkhashps(config, request));
     obj.pushKV("pooledtx", uint64_t(g_mempool.size()));
     obj.pushKV("chain", config.GetChainParams().NetworkIDString());
     obj.pushKV("warnings", GetWarnings("statusbar"));
 
     return obj;
 }
 
 // NOTE: Unlike wallet RPC (which use BCH values), mining RPCs follow GBT (BIP
 // 22) in using satoshi amounts
 static UniValue prioritisetransaction(const Config &config,
                                       const JSONRPCRequest &request) {
     if (request.fHelp || request.params.size() != 3) {
         throw std::runtime_error(RPCHelpMan{
             "prioritisetransaction",
             "Accepts the transaction into mined blocks at a higher "
             "(or lower) priority\n",
             {
-                {"txid", RPCArg::Type::STR_HEX, /* opt */ false,
-                 /* default_val */ "", "The transaction id."},
-                {"dummy", RPCArg::Type::NUM, /* opt */ true,
-                 /* default_val */ "null",
+                {"txid", RPCArg::Type::STR_HEX, RPCArg::Optional::NO,
+                 "The transaction id."},
+                {"dummy", RPCArg::Type::NUM,
+                 RPCArg::Optional::OMITTED_NAMED_ARG,
                  "API-Compatibility for previous API. Must be zero or "
                  "null.\n"
                  "                  DEPRECATED. For forward compatibility "
                  "use named arguments and omit this parameter."},
-                {"fee_delta", RPCArg::Type::NUM, /* opt */ false,
-                 /* default_val */ "",
+                {"fee_delta", RPCArg::Type::NUM, RPCArg::Optional::NO,
                  "The fee value (in satoshis) to add (or subtract, if "
                  "negative).\n"
                  "                        The fee is not actually paid, "
                  "only the algorithm for selecting transactions into a "
                  "block\n"
                  "                  considers the transaction as it would "
                  "have paid a higher (or lower) fee."},
             },
             RPCResult{"true              (boolean) Returns true\n"},
             RPCExamples{
                 HelpExampleCli("prioritisetransaction", "\"txid\" 0.0 10000") +
                 HelpExampleRpc("prioritisetransaction",
                                "\"txid\", 0.0, 10000")},
         }
                                      .ToString());
     }
 
     LOCK(cs_main);
 
     TxId txid(ParseHashV(request.params[0], "txid"));
     Amount nAmount = request.params[2].get_int64() * SATOSHI;
 
     if (!(request.params[1].isNull() || request.params[1].get_real() == 0)) {
         throw JSONRPCError(RPC_INVALID_PARAMETER,
                            "Priority is no longer supported, dummy argument to "
                            "prioritisetransaction must be 0.");
     }
 
     g_mempool.PrioritiseTransaction(txid, nAmount);
     return true;
 }
 
 // NOTE: Assumes a conclusive result; if result is inconclusive, it must be
 // handled by caller
 static UniValue BIP22ValidationResult(const Config &config,
                                       const CValidationState &state) {
     if (state.IsValid()) {
         return NullUniValue;
     }
 
     if (state.IsError()) {
         throw JSONRPCError(RPC_VERIFY_ERROR, FormatStateMessage(state));
     }
 
     if (state.IsInvalid()) {
         std::string strRejectReason = state.GetRejectReason();
         if (strRejectReason.empty()) {
             return "rejected";
         }
         return strRejectReason;
     }
 
     // Should be impossible.
     return "valid?";
 }
 
 static UniValue getblocktemplate(const Config &config,
                                  const JSONRPCRequest &request) {
     if (request.fHelp || request.params.size() > 1) {
         throw std::runtime_error(RPCHelpMan{
             "getblocktemplate",
             "\nIf the request parameters include a 'mode' key, that is "
             "used to explicitly select between the default 'template' "
             "request or a 'proposal'.\n"
             "It returns data needed to construct a block to work on.\n"
             "For full specification, see BIPs 22, 23, 9, and 145:\n"
             "    "
             "https://github.com/bitcoin/bips/blob/master/"
             "bip-0022.mediawiki\n"
             "    "
             "https://github.com/bitcoin/bips/blob/master/"
             "bip-0023.mediawiki\n"
             "    "
             "https://github.com/bitcoin/bips/blob/master/"
             "bip-0009.mediawiki#getblocktemplate_changes\n"
             "    ",
             {
                 {"template_request",
                  RPCArg::Type::OBJ,
-                 /* opt */ true,
-                 /* default_val */ "",
+                 "{}",
                  "A json object in the following spec",
                  {
-                     {"mode", RPCArg::Type::STR, /* opt */ true,
-                      /* default_val */ "",
+                     {"mode", RPCArg::Type::STR, /* treat as named arg */
+                      RPCArg::Optional::OMITTED_NAMED_ARG,
                       "This must be set to \"template\", \"proposal\" (see "
                       "BIP 23), or omitted"},
                      {
                          "capabilities",
                          RPCArg::Type::ARR,
-                         /* opt */ true,
-                         /* default_val */ "",
+                         /* treat as named arg */
+                         RPCArg::Optional::OMITTED_NAMED_ARG,
                          "A list of strings",
                          {
-                             {"support", RPCArg::Type::STR, /* opt */ true,
-                              /* default_val */ "",
+                             {"support", RPCArg::Type::STR,
+                              RPCArg::Optional::OMITTED,
                               "client side supported feature, 'longpoll', "
                               "'coinbasetxn', 'coinbasevalue', 'proposal', "
                               "'serverlist', 'workid'"},
                          },
                      },
                  },
                  "\"template_request\""},
             },
             RPCResult{
                 "{\n"
                 "  \"version\" : n,                    (numeric) The preferred "
                 "block version\n"
                 "  \"previousblockhash\" : \"xxxx\",     (string) The hash of "
                 "current highest block\n"
                 "  \"transactions\" : [                (array) contents of "
                 "non-coinbase transactions that should be included in the next "
                 "block\n"
                 "      {\n"
                 "         \"data\" : \"xxxx\",             (string) "
                 "transaction data encoded in hexadecimal (byte-for-byte)\n"
                 "         \"txid\" : \"xxxx\",             (string) "
                 "transaction id encoded in little-endian hexadecimal\n"
                 "         \"hash\" : \"xxxx\",             (string) hash "
                 "encoded in little-endian hexadecimal (including witness "
                 "data)\n"
                 "         \"depends\" : [                (array) array of "
                 "numbers \n"
                 "             n                          (numeric) "
                 "transactions before this one (by 1-based index in "
                 "'transactions' list) that must be present in the final block "
                 "if this one is\n"
                 "             ,...\n"
                 "         ],\n"
                 "         \"fee\": n,                    (numeric) difference "
                 "in value between transaction inputs and outputs (in "
                 "satoshis); for coinbase transactions, this is a negative "
                 "Number of the total collected block fees (ie, not including "
                 "the block subsidy); if key is not present, fee is unknown and "
                 "clients MUST NOT assume there isn't one\n"
                 "         \"sigops\" : n,                (numeric) total "
                 "SigOps count, as counted for purposes of block limits; if key "
                 "is not present, sigop count is unknown and clients MUST NOT "
                 "assume it is zero\n"
                 "      }\n"
                 "      ,...\n"
                 "  ],\n"
                 "  \"coinbaseaux\" : {                 (json object) data that "
                 "should be included in the coinbase's scriptSig content\n"
                 "      \"flags\" : \"xx\"                  (string) key name "
                 "is to be ignored, and value included in scriptSig\n"
                 "  },\n"
                 "  \"coinbasevalue\" : n,              (numeric) maximum "
                 "allowable input to coinbase transaction, including the "
                 "generation award and transaction fees (in satoshis)\n"
                 "  \"coinbasetxn\" : { ... },          (json object) "
                 "information for coinbase transaction\n"
                 "  \"target\" : \"xxxx\",                (string) The hash "
                 "target\n"
                 "  \"mintime\" : xxx,                  (numeric) The minimum "
                 "timestamp appropriate for next block time in seconds since "
                 "epoch (Jan 1 1970 GMT)\n"
                 "  \"mutable\" : [                     (array of string) list "
                 "of ways the block template may be changed \n"
                 "     \"value\"                          (string) A way the "
                 "block template may be changed, e.g. 'time', 'transactions', "
                 "'prevblock'\n"
                 "     ,...\n"
                 "  ],\n"
                 "  \"noncerange\" : \"00000000ffffffff\",(string) A range of "
                 "valid nonces\n"
                 "  \"sigoplimit\" : n,                 (numeric) limit of "
                 "sigops in blocks\n"
                 "  \"sizelimit\" : n,                  (numeric) limit of "
                 "block size\n"
                 "  \"curtime\" : ttt,                  (numeric) current "
                 "timestamp in seconds since epoch (Jan 1 1970 GMT)\n"
                 "  \"bits\" : \"xxxxxxxx\",              (string) compressed "
                 "target of next block\n"
                 "  \"height\" : n                      (numeric) The height of "
                 "the next block\n"
                 "}\n"},
             RPCExamples{HelpExampleCli("getblocktemplate", "") +
                         HelpExampleRpc("getblocktemplate", "")},
         }
                                      .ToString());
     }
 
     LOCK(cs_main);
 
     std::string strMode = "template";
     UniValue lpval = NullUniValue;
     std::set<std::string> setClientRules;
     if (!request.params[0].isNull()) {
         const UniValue &oparam = request.params[0].get_obj();
         const UniValue &modeval = find_value(oparam, "mode");
         if (modeval.isStr()) {
             strMode = modeval.get_str();
         } else if (modeval.isNull()) {
             /* Do nothing */
         } else {
             throw JSONRPCError(RPC_INVALID_PARAMETER, "Invalid mode");
         }
         lpval = find_value(oparam, "longpollid");
 
         if (strMode == "proposal") {
             const UniValue &dataval = find_value(oparam, "data");
             if (!dataval.isStr()) {
                 throw JSONRPCError(RPC_TYPE_ERROR,
                                    "Missing data String key for proposal");
             }
 
             CBlock block;
             if (!DecodeHexBlk(block, dataval.get_str())) {
                 throw JSONRPCError(RPC_DESERIALIZATION_ERROR,
                                    "Block decode failed");
             }
 
             const BlockHash hash = block.GetHash();
             const CBlockIndex *pindex = LookupBlockIndex(hash);
             if (pindex) {
                 if (pindex->IsValid(BlockValidity::SCRIPTS)) {
                     return "duplicate";
                 }
                 if (pindex->nStatus.isInvalid()) {
                     return "duplicate-invalid";
                 }
                 return "duplicate-inconclusive";
             }
 
             CBlockIndex *const pindexPrev = ::ChainActive().Tip();
             // TestBlockValidity only supports blocks built on the current Tip
             if (block.hashPrevBlock != pindexPrev->GetBlockHash()) {
                 return "inconclusive-not-best-prevblk";
             }
             CValidationState state;
             TestBlockValidity(state, config.GetChainParams(), block, pindexPrev,
                               BlockValidationOptions(config)
                                   .withCheckPoW(false)
                                   .withCheckMerkleRoot(true));
             return BIP22ValidationResult(config, state);
         }
     }
 
     if (strMode != "template") {
         throw JSONRPCError(RPC_INVALID_PARAMETER, "Invalid mode");
     }
 
     if (!g_connman) {
         throw JSONRPCError(
             RPC_CLIENT_P2P_DISABLED,
             "Error: Peer-to-peer functionality missing or disabled");
     }
 
     if (g_connman->GetNodeCount(CConnman::CONNECTIONS_ALL) == 0) {
         throw JSONRPCError(RPC_CLIENT_NOT_CONNECTED,
                            "Bitcoin is not connected!");
     }
 
     if (::ChainstateActive().IsInitialBlockDownload()) {
         throw JSONRPCError(RPC_CLIENT_IN_INITIAL_DOWNLOAD, PACKAGE_NAME
                            " is in initial sync and waiting for blocks...");
     }
 
     static unsigned int nTransactionsUpdatedLast;
 
     if (!lpval.isNull()) {
         // Wait to respond until either the best block changes, OR a minute has
         // passed and there are more transactions
         uint256 hashWatchedChain;
         std::chrono::steady_clock::time_point checktxtime;
         unsigned int nTransactionsUpdatedLastLP;
 
         if (lpval.isStr()) {
             // Format: <hashBestChain><nTransactionsUpdatedLast>
             std::string lpstr = lpval.get_str();
 
             hashWatchedChain = ParseHashV(lpstr.substr(0, 64), "longpollid");
             nTransactionsUpdatedLastLP = atoi64(lpstr.substr(64));
         } else {
             // NOTE: Spec does not specify behaviour for non-string longpollid,
             // but this makes testing easier
             hashWatchedChain = ::ChainActive().Tip()->GetBlockHash();
             nTransactionsUpdatedLastLP = nTransactionsUpdatedLast;
         }
 
         // Release the wallet and main lock while waiting
         LEAVE_CRITICAL_SECTION(cs_main);
         {
             checktxtime =
                 std::chrono::steady_clock::now() + std::chrono::minutes(1);
 
             WAIT_LOCK(g_best_block_mutex, lock);
             while (g_best_block == hashWatchedChain && IsRPCRunning()) {
                 if (g_best_block_cv.wait_until(lock, checktxtime) ==
                     std::cv_status::timeout) {
                     // Timeout: Check transactions for update
                     if (g_mempool.GetTransactionsUpdated() !=
                         nTransactionsUpdatedLastLP) {
                         break;
                     }
                     checktxtime += std::chrono::seconds(10);
                 }
             }
         }
         ENTER_CRITICAL_SECTION(cs_main);
 
         if (!IsRPCRunning()) {
             throw JSONRPCError(RPC_CLIENT_NOT_CONNECTED, "Shutting down");
         }
         // TODO: Maybe recheck connections/IBD and (if something wrong) send an
         // expires-immediately template to stop miners?
     }
 
     // Update block
     static CBlockIndex *pindexPrev;
     static int64_t nStart;
     static std::unique_ptr<CBlockTemplate> pblocktemplate;
     if (pindexPrev != ::ChainActive().Tip() ||
         (g_mempool.GetTransactionsUpdated() != nTransactionsUpdatedLast &&
          GetTime() - nStart > 5)) {
         // Clear pindexPrev so future calls make a new block, despite any
         // failures from here on
         pindexPrev = nullptr;
 
         // Store the pindexBest used before CreateNewBlock, to avoid races
         nTransactionsUpdatedLast = g_mempool.GetTransactionsUpdated();
         CBlockIndex *pindexPrevNew = ::ChainActive().Tip();
         nStart = GetTime();
 
         // Create new block
         CScript scriptDummy = CScript() << OP_TRUE;
         pblocktemplate =
             BlockAssembler(config, g_mempool).CreateNewBlock(scriptDummy);
         if (!pblocktemplate) {
             throw JSONRPCError(RPC_OUT_OF_MEMORY, "Out of memory");
         }
 
         // Need to update only after we know CreateNewBlock succeeded
         pindexPrev = pindexPrevNew;
     }
 
     assert(pindexPrev);
     // pointer for convenience
     CBlock *pblock = &pblocktemplate->block;
 
     // Update nTime
     UpdateTime(pblock, config.GetChainParams().GetConsensus(), pindexPrev);
     pblock->nNonce = 0;
 
     UniValue aCaps(UniValue::VARR);
     aCaps.push_back("proposal");
 
     UniValue transactions(UniValue::VARR);
     transactions.reserve(pblock->vtx.size());
     int index_in_template = 0;
     for (const auto &it : pblock->vtx) {
         const CTransaction &tx = *it;
         uint256 txId = tx.GetId();
 
         if (tx.IsCoinBase()) {
             index_in_template++;
             continue;
         }
 
         UniValue entry(UniValue::VOBJ);
         entry.reserve(5);
         entry.__pushKV("data", EncodeHexTx(tx));
         entry.__pushKV("txid", txId.GetHex());
         entry.__pushKV("hash", tx.GetHash().GetHex());
         entry.__pushKV("fee", pblocktemplate->entries[index_in_template].fees /
                                   SATOSHI);
         int64_t nTxSigOps =
             pblocktemplate->entries[index_in_template].sigOpCount;
         entry.__pushKV("sigops", nTxSigOps);
 
         transactions.push_back(entry);
         index_in_template++;
     }
 
     UniValue aux(UniValue::VOBJ);
     aux.pushKV("flags", HexStr(COINBASE_FLAGS.begin(), COINBASE_FLAGS.end()));
 
     arith_uint256 hashTarget = arith_uint256().SetCompact(pblock->nBits);
 
     UniValue aMutable(UniValue::VARR);
     aMutable.push_back("time");
     aMutable.push_back("transactions");
     aMutable.push_back("prevblock");
 
     UniValue result(UniValue::VOBJ);
     result.pushKV("capabilities", aCaps);
 
     result.pushKV("version", pblock->nVersion);
 
     result.pushKV("previousblockhash", pblock->hashPrevBlock.GetHex());
     result.pushKV("transactions", transactions);
     result.pushKV("coinbaseaux", aux);
     result.pushKV("coinbasevalue",
                   int64_t(pblock->vtx[0]->vout[0].nValue / SATOSHI));
     result.pushKV("longpollid", ::ChainActive().Tip()->GetBlockHash().GetHex() +
                                     i64tostr(nTransactionsUpdatedLast));
     result.pushKV("target", hashTarget.GetHex());
     result.pushKV("mintime", int64_t(pindexPrev->GetMedianTimePast()) + 1);
     result.pushKV("mutable", aMutable);
     result.pushKV("noncerange", "00000000ffffffff");
     result.pushKV("sigoplimit",
                   GetMaxBlockSigChecksCount(DEFAULT_MAX_BLOCK_SIZE));
     result.pushKV("sizelimit", DEFAULT_MAX_BLOCK_SIZE);
     result.pushKV("curtime", pblock->GetBlockTime());
     result.pushKV("bits", strprintf("%08x", pblock->nBits));
     result.pushKV("height", int64_t(pindexPrev->nHeight) + 1);
 
     return result;
 }
 
 class submitblock_StateCatcher : public CValidationInterface {
 public:
     uint256 hash;
     bool found;
     CValidationState state;
 
     explicit submitblock_StateCatcher(const uint256 &hashIn)
         : hash(hashIn), found(false), state() {}
 
 protected:
     void BlockChecked(const CBlock &block,
                       const CValidationState &stateIn) override {
         if (block.GetHash() != hash) {
             return;
         }
 
         found = true;
         state = stateIn;
     }
 };
 
 static UniValue submitblock(const Config &config,
                             const JSONRPCRequest &request) {
     // We allow 2 arguments for compliance with BIP22. Argument 2 is ignored.
     if (request.fHelp || request.params.size() < 1 ||
         request.params.size() > 2) {
         throw std::runtime_error(RPCHelpMan{
             "submitblock",
             "\nAttempts to submit new block to network.\n"
             "See https://en.bitcoin.it/wiki/BIP_0022 for full "
             "specification.\n",
             {
-                {"hexdata", RPCArg::Type::STR_HEX, /* opt */ false,
-                 /* default_val */ "", "the hex-encoded block data to submit"},
-                {"dummy", RPCArg::Type::STR, /* opt */ true,
-                 /* default_val */ "ignored",
+                {"hexdata", RPCArg::Type::STR_HEX, RPCArg::Optional::NO,
+                 "the hex-encoded block data to submit"},
+                {"dummy", RPCArg::Type::STR, /* default */ "ignored",
                  "dummy value, for compatibility with BIP22. This value is "
                  "ignored."},
             },
             RPCResults{},
             RPCExamples{HelpExampleCli("submitblock", "\"mydata\"") +
                         HelpExampleRpc("submitblock", "\"mydata\"")},
         }
                                      .ToString());
     }
 
     std::shared_ptr<CBlock> blockptr = std::make_shared<CBlock>();
     CBlock &block = *blockptr;
     if (!DecodeHexBlk(block, request.params[0].get_str())) {
         throw JSONRPCError(RPC_DESERIALIZATION_ERROR, "Block decode failed");
     }
 
     if (block.vtx.empty() || !block.vtx[0]->IsCoinBase()) {
         throw JSONRPCError(RPC_DESERIALIZATION_ERROR,
                            "Block does not start with a coinbase");
     }
 
     const BlockHash hash = block.GetHash();
     {
         LOCK(cs_main);
         const CBlockIndex *pindex = LookupBlockIndex(hash);
         if (pindex) {
             if (pindex->IsValid(BlockValidity::SCRIPTS)) {
                 return "duplicate";
             }
             if (pindex->nStatus.isInvalid()) {
                 return "duplicate-invalid";
             }
         }
     }
 
     bool new_block;
     submitblock_StateCatcher sc(block.GetHash());
     RegisterValidationInterface(&sc);
     bool accepted =
         ProcessNewBlock(config, blockptr, /* fForceProcessing */ true,
                         /* fNewBlock */ &new_block);
     // We are only interested in BlockChecked which will have been dispatched
     // in-thread, so no need to sync before unregistering.
     UnregisterValidationInterface(&sc);
     // Sync to ensure that the catcher's slots aren't executing when it goes out
     // of scope and is deleted.
     SyncWithValidationInterfaceQueue();
     if (!new_block && accepted) {
         return "duplicate";
     }
 
     if (!sc.found) {
         return "inconclusive";
     }
 
     return BIP22ValidationResult(config, sc.state);
 }
 
 static UniValue submitheader(const Config &config,
                              const JSONRPCRequest &request) {
     if (request.fHelp || request.params.size() != 1) {
         throw std::runtime_error(RPCHelpMan{
             "submitheader",
             "\nDecode the given hexdata as a header and submit it as a "
             "candidate chain tip if valid."
             "\nThrows when the header is invalid.\n",
             {
-                {"hexdata", RPCArg::Type::STR_HEX, /* opt */ false,
-                 /* default_val */ "", "the hex-encoded block header data"},
+                {"hexdata", RPCArg::Type::STR_HEX, RPCArg::Optional::NO,
+                 "the hex-encoded block header data"},
             },
             RPCResult{"None"},
             RPCExamples{HelpExampleCli("submitheader", "\"aabbcc\"") +
                         HelpExampleRpc("submitheader", "\"aabbcc\"")},
         }
                                      .ToString());
     }
 
     CBlockHeader h;
     if (!DecodeHexBlockHeader(h, request.params[0].get_str())) {
         throw JSONRPCError(RPC_DESERIALIZATION_ERROR,
                            "Block header decode failed");
     }
     {
         LOCK(cs_main);
         if (!LookupBlockIndex(h.hashPrevBlock)) {
             throw JSONRPCError(RPC_VERIFY_ERROR,
                                "Must submit previous header (" +
                                    h.hashPrevBlock.GetHex() + ") first");
         }
     }
 
     CValidationState state;
     ProcessNewBlockHeaders(config, {h}, state, /* ppindex */ nullptr,
                            /* first_invalid */ nullptr);
     if (state.IsValid()) {
         return NullUniValue;
     }
     if (state.IsError()) {
         throw JSONRPCError(RPC_VERIFY_ERROR, FormatStateMessage(state));
     }
     throw JSONRPCError(RPC_VERIFY_ERROR, state.GetRejectReason());
 }
 
 static UniValue estimatefee(const Config &config,
                             const JSONRPCRequest &request) {
     if (request.fHelp || request.params.size() > 0) {
         throw std::runtime_error(RPCHelpMan{
             "estimatefee",
             "\nEstimates the approximate fee per kilobyte needed "
             "for a transaction\n",
             {},
             RPCResult{"n              (numeric) estimated fee-per-kilobyte\n"},
             RPCExamples{HelpExampleCli("estimatefee", "")},
         }
                                      .ToString());
     }
 
     return ValueFromAmount(g_mempool.estimateFee().GetFeePerK());
 }
 
 // clang-format off
 static const CRPCCommand commands[] = {
     //  category   name                     actor (function)       argNames
     //  ---------- ------------------------ ---------------------- ----------
     {"mining",     "getnetworkhashps",      getnetworkhashps,      {"nblocks", "height"}},
     {"mining",     "getmininginfo",         getmininginfo,         {}},
     {"mining",     "prioritisetransaction", prioritisetransaction, {"txid", "dummy", "fee_delta"}},
     {"mining",     "getblocktemplate",      getblocktemplate,      {"template_request"}},
     {"mining",     "submitblock",           submitblock,           {"hexdata", "dummy"}},
     {"mining",     "submitheader",          submitheader,          {"hexdata"}},
 
     {"generating", "generatetoaddress",     generatetoaddress,     {"nblocks", "address", "maxtries"}},
 
     {"util",       "estimatefee",           estimatefee,           {"nblocks"}},
 };
 // clang-format on
 
 void RegisterMiningRPCCommands(CRPCTable &t) {
     for (unsigned int vcidx = 0; vcidx < ARRAYLEN(commands); vcidx++) {
         t.appendCommand(commands[vcidx].name, &commands[vcidx]);
     }
 }
diff --git a/src/rpc/misc.cpp b/src/rpc/misc.cpp
index 56885fcf6..2fc99a3ff 100644
--- a/src/rpc/misc.cpp
+++ b/src/rpc/misc.cpp
@@ -1,714 +1,707 @@
 // Copyright (c) 2010 Satoshi Nakamoto
 // Copyright (c) 2009-2016 The Bitcoin Core developers
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
 #include <chain.h>
 #include <clientversion.h>
 #include <config.h>
 #include <core_io.h>
 #include <httpserver.h>
 #include <key_io.h>
 #include <logging.h>
 #include <net.h>
 #include <netbase.h>
 #include <outputtype.h>
 #include <rpc/blockchain.h>
 #include <rpc/server.h>
 #include <rpc/util.h>
 #include <script/descriptor.h>
 #include <timedata.h>
 #include <util/check.h>
 #include <util/strencodings.h>
 #include <util/system.h>
 #include <util/validation.h>
 #include <validation.h>
 #include <warnings.h>
 
 #include <univalue.h>
 
 #include <cstdint>
 #ifdef HAVE_MALLOC_INFO
 #include <malloc.h>
 #endif
 
 static UniValue validateaddress(const Config &config,
                                 const JSONRPCRequest &request) {
     if (request.fHelp || request.params.size() != 1) {
         throw std::runtime_error(RPCHelpMan{
             "validateaddress",
             "\nReturn information about the given bitcoin address.\n",
             {
-                {"address", RPCArg::Type::STR, /* opt */ false,
-                 /* default_val */ "", "The bitcoin address to validate"},
+                {"address", RPCArg::Type::STR, RPCArg::Optional::NO,
+                 "The bitcoin address to validate"},
             },
             RPCResult{
                 "{\n"
                 "  \"isvalid\" : true|false,       (boolean) If the address is "
                 "valid or not. If not, this is the only property returned.\n"
                 "  \"address\" : \"address\",        (string) The bitcoin "
                 "address validated\n"
                 "  \"scriptPubKey\" : \"hex\",       (string) The hex-encoded "
                 "scriptPubKey generated by the address\n"
                 "  \"isscript\" : true|false,      (boolean) If the key is a "
                 "script\n"
                 "}\n"},
             RPCExamples{
                 HelpExampleCli("validateaddress",
                                "\"1PSSGeFHDnKNxiEyFrD1wcEaHr9hrQDDWc\"") +
                 HelpExampleRpc("validateaddress",
                                "\"1PSSGeFHDnKNxiEyFrD1wcEaHr9hrQDDWc\"")},
         }
                                      .ToString());
     }
 
     CTxDestination dest =
         DecodeDestination(request.params[0].get_str(), config.GetChainParams());
     bool isValid = IsValidDestination(dest);
 
     UniValue ret(UniValue::VOBJ);
     ret.pushKV("isvalid", isValid);
 
     if (isValid) {
         if (ret["address"].isNull()) {
             std::string currentAddress = EncodeDestination(dest, config);
             ret.pushKV("address", currentAddress);
 
             CScript scriptPubKey = GetScriptForDestination(dest);
             ret.pushKV("scriptPubKey",
                        HexStr(scriptPubKey.begin(), scriptPubKey.end()));
 
             UniValue detail = DescribeAddress(dest);
             ret.pushKVs(detail);
         }
     }
     return ret;
 }
 
 static UniValue createmultisig(const Config &config,
                                const JSONRPCRequest &request) {
     if (request.fHelp || request.params.size() < 2 ||
         request.params.size() > 2) {
         std::string msg =
             RPCHelpMan{
                 "createmultisig",
                 "\nCreates a multi-signature address with n signature of m "
                 "keys required.\n"
                 "It returns a json object with the address and redeemScript.\n",
                 {
-                    {"nrequired", RPCArg::Type::NUM, /* opt */ false,
-                     /* default_val */ "",
+                    {"nrequired", RPCArg::Type::NUM, RPCArg::Optional::NO,
                      "The number of required signatures out of the n keys."},
                     {"keys",
                      RPCArg::Type::ARR,
-                     /* opt */ false,
-                     /* default_val */ "",
+                     RPCArg::Optional::NO,
                      "A json array of hex-encoded public keys.",
                      {
-                         {"key", RPCArg::Type::STR_HEX, /* opt */ false,
-                          /* default_val */ "", "The hex-encoded public key"},
+                         {"key", RPCArg::Type::STR_HEX,
+                          RPCArg::Optional::OMITTED,
+                          "The hex-encoded public key"},
                      }},
                 },
                 RPCResult{"{\n"
                           "  \"address\":\"multisigaddress\",  (string) The "
                           "value of the new multisig address.\n"
                           "  \"redeemScript\":\"script\"       (string) The "
                           "string value of the hex-encoded redemption script.\n"
                           "}\n"},
                 RPCExamples{
                     "\nCreate a multisig address from 2 public keys\n" +
                     HelpExampleCli(
                         "createmultisig",
                         "2 "
                         "\"["
                         "\\\"03789ed0bb717d88f7d321a368d905e7430207ebbd82bd3"
                         "42cf11ae157a7ace5fd\\\","
                         "\\\"03dbc6764b8884a92e871274b87583e6d5c2a58819473e1"
                         "7e107ef3f6aa5a61626\\\"]\"") +
                     "\nAs a JSON-RPC call\n" +
                     HelpExampleRpc(
                         "createmultisig",
                         "2, "
                         "\"["
                         "\\\"03789ed0bb717d88f7d321a368d905e7430207ebbd82bd3"
                         "42cf11ae157a7ace5fd\\\","
                         "\\\"03dbc6764b8884a92e871274b87583e6d5c2a58819473e1"
                         "7e107ef3f6aa5a61626\\\"]\"")},
             }
                 .ToString();
         throw std::runtime_error(msg);
     }
 
     int required = request.params[0].get_int();
 
     // Get the public keys
     const UniValue &keys = request.params[1].get_array();
     std::vector<CPubKey> pubkeys;
     for (size_t i = 0; i < keys.size(); ++i) {
         if ((keys[i].get_str().length() ==
                  2 * CPubKey::COMPRESSED_PUBLIC_KEY_SIZE ||
              keys[i].get_str().length() == 2 * CPubKey::PUBLIC_KEY_SIZE) &&
             IsHex(keys[i].get_str())) {
             pubkeys.push_back(HexToPubKey(keys[i].get_str()));
         } else {
             throw JSONRPCError(
                 RPC_INVALID_ADDRESS_OR_KEY,
                 strprintf("Invalid public key: %s\n", keys[i].get_str()));
         }
     }
 
     // Get the output type
     OutputType output_type = OutputType::LEGACY;
 
     // Construct using pay-to-script-hash:
     const CScript inner = CreateMultisigRedeemscript(required, pubkeys);
     CBasicKeyStore keystore;
     const CTxDestination dest =
         AddAndGetDestinationForScript(keystore, inner, output_type);
 
     UniValue result(UniValue::VOBJ);
     result.pushKV("address", EncodeDestination(dest, config));
     result.pushKV("redeemScript", HexStr(inner.begin(), inner.end()));
 
     return result;
 }
 
 UniValue deriveaddresses(const Config &config, const JSONRPCRequest &request) {
     if (request.fHelp || request.params.empty() || request.params.size() > 3) {
         throw std::runtime_error(RPCHelpMan{
             "deriveaddresses",
             {"\nDerives one or more addresses corresponding to an output "
              "descriptor.\n"
              "Examples of output descriptors are:\n"
              "    pkh(<pubkey>)                        P2PKH outputs for the "
              "given pubkey\n"
              "    sh(multi(<n>,<pubkey>,<pubkey>,...)) P2SH-multisig outputs "
              "for the given threshold and pubkeys\n"
              "    raw(<hex script>)                    Outputs whose "
              "scriptPubKey equals the specified hex scripts\n"
              "\nIn the above, <pubkey> either refers to a fixed public key in "
              "hexadecimal notation, or to an xpub/xprv optionally followed by "
              "one\n"
              "or more path elements separated by \"/\", where \"h\" represents "
              "a hardened child key.\n"
              "For more information on output descriptors, see the "
              "documentation in the doc/descriptors.md file.\n"},
-            {{"descriptor", RPCArg::Type::STR, /* opt */ false,
-              /* default_val */ "", "The descriptor."},
-             {"begin", RPCArg::Type::NUM, /* opt */ true, /* default_val */ "",
-              "If a ranged descriptor is used, this specifies the beginning of "
-              "the range to import."},
-             {"end", RPCArg::Type::NUM, /* opt */ true, /* default_val */ "",
-              "If a ranged descriptor is used, this specifies the end of the "
-              "range to import."}},
+            {
+                {"descriptor", RPCArg::Type::STR, RPCArg::Optional::NO,
+                 "The descriptor."},
+                {"begin", RPCArg::Type::NUM,
+                 RPCArg::Optional::OMITTED_NAMED_ARG,
+                 "If a ranged descriptor is used, this specifies the beginning "
+                 "of the range to import."},
+                {"end", RPCArg::Type::NUM, RPCArg::Optional::OMITTED_NAMED_ARG,
+                 "If a ranged descriptor is used, this specifies the end of "
+                 "the range to import."},
+            },
             RPCResult{"[ address ] (array) the derived addresses\n"},
             RPCExamples{
                 "First three native segwit receive addresses\n" +
                 HelpExampleCli(
                     "deriveaddresses",
                     "\"pkh([d34db33f/84h/0h/"
                     "0h]"
                     "xpub6DJ2dNUysrn5Vt36jH2KLBT2i1auw1tTSSomg8PhqNiUtx8QX2SvC9"
                     "nrHu81fT41fvDUnhMjEzQgXnQjKEu3oaqMSzhSrHMxyyoEAmUHQbY/0/"
                     "*)\" 0 2")}}.ToString());
     }
 
     RPCTypeCheck(request.params,
                  {UniValue::VSTR, UniValue::VNUM, UniValue::VNUM});
     const std::string desc_str = request.params[0].get_str();
 
     int range_begin = 0;
     int range_end = 0;
 
     if (request.params.size() >= 2) {
         if (request.params.size() == 2) {
             throw JSONRPCError(RPC_INVALID_PARAMETER,
                                "Missing range end parameter");
         }
         range_begin = request.params[1].get_int();
         range_end = request.params[2].get_int();
         if (range_begin < 0) {
             throw JSONRPCError(RPC_INVALID_PARAMETER,
                                "Range should be greater or equal than 0");
         }
         if (range_begin > range_end) {
             throw JSONRPCError(
                 RPC_INVALID_PARAMETER,
                 "Range end should be equal to or greater than begin");
         }
     }
 
     FlatSigningProvider provider;
     auto desc = Parse(desc_str, provider);
     if (!desc) {
         throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY,
                            strprintf("Invalid descriptor"));
     }
 
     if (!desc->IsRange() && request.params.size() > 1) {
         throw JSONRPCError(
             RPC_INVALID_PARAMETER,
             "Range should not be specified for an un-ranged descriptor");
     }
 
     if (desc->IsRange() && request.params.size() == 1) {
         throw JSONRPCError(RPC_INVALID_PARAMETER,
                            "Range must be specified for a ranged descriptor");
     }
 
     UniValue addresses(UniValue::VARR);
 
     for (int i = range_begin; i <= range_end; ++i) {
         std::vector<CScript> scripts;
         if (!desc->Expand(i, provider, scripts, provider)) {
             throw JSONRPCError(
                 RPC_INVALID_ADDRESS_OR_KEY,
                 strprintf("Cannot derive script without private keys"));
         }
 
         for (const CScript &script : scripts) {
             CTxDestination dest;
             if (!ExtractDestination(script, dest)) {
                 throw JSONRPCError(
                     RPC_INVALID_ADDRESS_OR_KEY,
                     strprintf(
                         "Descriptor does not have a corresponding address"));
             }
 
             addresses.push_back(EncodeDestination(dest, config));
         }
     }
 
     // This should not be possible, but an assert seems overkill:
     if (addresses.empty()) {
         throw JSONRPCError(RPC_MISC_ERROR, "Unexpected empty result");
     }
 
     return addresses;
 }
 
 static UniValue verifymessage(const Config &config,
                               const JSONRPCRequest &request) {
     if (request.fHelp || request.params.size() != 3) {
         throw std::runtime_error(RPCHelpMan{
             "verifymessage",
             "\nVerify a signed message\n",
             {
-                {"address", RPCArg::Type::STR, /* opt */ false,
-                 /* default_val */ "",
+                {"address", RPCArg::Type::STR, RPCArg::Optional::NO,
                  "The bitcoin address to use for the signature."},
-                {"signature", RPCArg::Type::STR, /* opt */ false,
-                 /* default_val */ "",
+                {"signature", RPCArg::Type::STR, RPCArg::Optional::NO,
                  "The signature provided by the signer in base 64 encoding "
                  "(see signmessage)."},
-                {"message", RPCArg::Type::STR, /* opt */ false,
-                 /* default_val */ "", "The message that was signed."},
+                {"message", RPCArg::Type::STR, RPCArg::Optional::NO,
+                 "The message that was signed."},
             },
             RPCResult{"true|false   (boolean) If the signature is verified or "
                       "not.\n"},
             RPCExamples{
                 "\nUnlock the wallet for 30 seconds\n" +
                 HelpExampleCli("walletpassphrase", "\"mypassphrase\" 30") +
                 "\nCreate the signature\n" +
                 HelpExampleCli(
                     "signmessage",
                     "\"1D1ZrZNe3JUo7ZycKEYQQiQAWd9y54F4XX\" \"my message\"") +
                 "\nVerify the signature\n" +
                 HelpExampleCli("verifymessage",
                                "\"1D1ZrZNe3JUo7ZycKEYQQiQAWd9y54F4"
                                "XX\" \"signature\" \"my "
                                "message\"") +
                 "\nAs a JSON-RPC call\n" +
                 HelpExampleRpc("verifymessage",
                                "\"1D1ZrZNe3JUo7ZycKEYQQiQAWd9y54F4"
                                "XX\", \"signature\", \"my "
                                "message\"")},
         }
                                      .ToString());
     }
 
     LOCK(cs_main);
 
     std::string strAddress = request.params[0].get_str();
     std::string strSign = request.params[1].get_str();
     std::string strMessage = request.params[2].get_str();
 
     CTxDestination destination =
         DecodeDestination(strAddress, config.GetChainParams());
     if (!IsValidDestination(destination)) {
         throw JSONRPCError(RPC_TYPE_ERROR, "Invalid address");
     }
 
     const CKeyID *keyID = boost::get<CKeyID>(&destination);
     if (!keyID) {
         throw JSONRPCError(RPC_TYPE_ERROR, "Address does not refer to key");
     }
 
     bool fInvalid = false;
     std::vector<uint8_t> vchSig = DecodeBase64(strSign.c_str(), &fInvalid);
 
     if (fInvalid) {
         throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY,
                            "Malformed base64 encoding");
     }
 
     CHashWriter ss(SER_GETHASH, 0);
     ss << strMessageMagic;
     ss << strMessage;
 
     CPubKey pubkey;
     if (!pubkey.RecoverCompact(ss.GetHash(), vchSig)) {
         return false;
     }
 
     return (pubkey.GetID() == *keyID);
 }
 
 static UniValue signmessagewithprivkey(const Config &config,
                                        const JSONRPCRequest &request) {
     if (request.fHelp || request.params.size() != 2) {
         throw std::runtime_error(RPCHelpMan{
             "signmessagewithprivkey",
             "\nSign a message with the private key of an address\n",
             {
-                {"privkey", RPCArg::Type::STR, /* opt */ false,
-                 /* default_val */ "",
+                {"privkey", RPCArg::Type::STR, RPCArg::Optional::NO,
                  "The private key to sign the message with."},
-                {"message", RPCArg::Type::STR, /* opt */ false,
-                 /* default_val */ "", "The message to create a signature of."},
+                {"message", RPCArg::Type::STR, RPCArg::Optional::NO,
+                 "The message to create a signature of."},
             },
             RPCResult{"\"signature\"          (string) The signature of the "
                       "message encoded in base 64\n"},
             RPCExamples{"\nCreate the signature\n" +
                         HelpExampleCli("signmessagewithprivkey",
                                        "\"privkey\" \"my message\"") +
                         "\nVerify the signature\n" +
                         HelpExampleCli("verifymessage",
                                        "\"1D1ZrZNe3JUo7ZycKEYQQiQAWd9y54F4"
                                        "XX\" \"signature\" \"my "
                                        "message\"") +
                         "\nAs a JSON-RPC call\n" +
                         HelpExampleRpc("signmessagewithprivkey",
                                        "\"privkey\", \"my message\"")},
         }
                                      .ToString());
     }
 
     std::string strPrivkey = request.params[0].get_str();
     std::string strMessage = request.params[1].get_str();
 
     CKey key = DecodeSecret(strPrivkey);
     if (!key.IsValid()) {
         throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Invalid private key");
     }
 
     CHashWriter ss(SER_GETHASH, 0);
     ss << strMessageMagic;
     ss << strMessage;
 
     std::vector<uint8_t> vchSig;
     if (!key.SignCompact(ss.GetHash(), vchSig)) {
         throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Sign failed");
     }
 
     return EncodeBase64(vchSig.data(), vchSig.size());
 }
 
 static UniValue setmocktime(const Config &config,
                             const JSONRPCRequest &request) {
     if (request.fHelp || request.params.size() != 1) {
         throw std::runtime_error(RPCHelpMan{
             "setmocktime",
             "\nSet the local time to given timestamp (-regtest only)\n",
             {
-                {"timestamp", RPCArg::Type::NUM, /* opt */ false,
-                 /* default_val */ "",
+                {"timestamp", RPCArg::Type::NUM, RPCArg::Optional::NO,
                  "Unix seconds-since-epoch timestamp\n"
                  "   Pass 0 to go back to using the system time."},
             },
             RPCResults{},
             RPCExamples{""},
         }
                                      .ToString());
     }
 
     if (!config.GetChainParams().MineBlocksOnDemand()) {
         throw std::runtime_error(
             "setmocktime for regression testing (-regtest mode) only");
     }
 
     // For now, don't change mocktime if we're in the middle of validation, as
     // this could have an effect on mempool time-based eviction, as well as
     // IsInitialBlockDownload().
     // TODO: figure out the right way to synchronize around mocktime, and
     // ensure all call sites of GetTime() are accessing this safely.
     LOCK(cs_main);
 
     RPCTypeCheck(request.params, {UniValue::VNUM});
     int64_t mockTime = request.params[0].get_int64();
     if (mockTime < 0) {
         throw JSONRPCError(RPC_INVALID_PARAMETER,
                            "Timestamp must be 0 or greater");
     }
     SetMockTime(mockTime);
 
     return NullUniValue;
 }
 
 static UniValue RPCLockedMemoryInfo() {
     LockedPool::Stats stats = LockedPoolManager::Instance().stats();
     UniValue obj(UniValue::VOBJ);
     obj.pushKV("used", uint64_t(stats.used));
     obj.pushKV("free", uint64_t(stats.free));
     obj.pushKV("total", uint64_t(stats.total));
     obj.pushKV("locked", uint64_t(stats.locked));
     obj.pushKV("chunks_used", uint64_t(stats.chunks_used));
     obj.pushKV("chunks_free", uint64_t(stats.chunks_free));
     return obj;
 }
 
 #ifdef HAVE_MALLOC_INFO
 static std::string RPCMallocInfo() {
     char *ptr = nullptr;
     size_t size = 0;
     FILE *f = open_memstream(&ptr, &size);
     if (f) {
         malloc_info(0, f);
         fclose(f);
         if (ptr) {
             std::string rv(ptr, size);
             free(ptr);
             return rv;
         }
     }
     return "";
 }
 #endif
 
 static UniValue getmemoryinfo(const Config &config,
                               const JSONRPCRequest &request) {
     /* Please, avoid using the word "pool" here in the RPC interface or help,
      * as users will undoubtedly confuse it with the other "memory pool"
      */
     if (request.fHelp || request.params.size() > 1) {
         throw std::runtime_error(RPCHelpMan{
             "getmemoryinfo",
             "Returns an object containing information about memory usage.\n",
             {
-                {"mode", RPCArg::Type::STR, /* opt */ true,
-                 /* default_val */ "\"stats\"",
+                {"mode", RPCArg::Type::STR, /* default */ "\"stats\"",
                  "determines what kind of information is returned.\n"
                  "  - \"stats\" returns general statistics about memory usage "
                  "in the daemon.\n"
                  "  - \"mallocinfo\" returns an XML string describing "
                  "low-level heap state (only available if compiled with glibc "
                  "2.10+)."},
             },
             {
                 RPCResult{"mode \"stats\"",
                           "{\n"
                           "  \"locked\": {               (json object) "
                           "Information about locked memory manager\n"
                           "    \"used\": xxxxx,          (numeric) Number of "
                           "bytes used\n"
                           "    \"free\": xxxxx,          (numeric) Number of "
                           "bytes available in current arenas\n"
                           "    \"total\": xxxxxxx,       (numeric) Total "
                           "number of bytes managed\n"
                           "    \"locked\": xxxxxx,       (numeric) Amount of "
                           "bytes that succeeded locking. If this number is "
                           "smaller than total, locking pages failed at some "
                           "point and key data could be swapped to disk.\n"
                           "    \"chunks_used\": xxxxx,   (numeric) Number "
                           "allocated chunks\n"
                           "    \"chunks_free\": xxxxx,   (numeric) Number "
                           "unused chunks\n"
                           "  }\n"
                           "}\n"},
                 RPCResult{"mode \"mallocinfo\"",
                           "\"<malloc version=\"1\">...\"\n"},
             },
             RPCExamples{HelpExampleCli("getmemoryinfo", "") +
                         HelpExampleRpc("getmemoryinfo", "")},
         }
                                      .ToString());
     }
 
     std::string mode =
         request.params[0].isNull() ? "stats" : request.params[0].get_str();
     if (mode == "stats") {
         UniValue obj(UniValue::VOBJ);
         obj.pushKV("locked", RPCLockedMemoryInfo());
         return obj;
     } else if (mode == "mallocinfo") {
 #ifdef HAVE_MALLOC_INFO
         return RPCMallocInfo();
 #else
         throw JSONRPCError(
             RPC_INVALID_PARAMETER,
             "mallocinfo is only available when compiled with glibc 2.10+");
 #endif
     } else {
         throw JSONRPCError(RPC_INVALID_PARAMETER, "unknown mode " + mode);
     }
 }
 
 static void EnableOrDisableLogCategories(UniValue cats, bool enable) {
     cats = cats.get_array();
     for (size_t i = 0; i < cats.size(); ++i) {
         std::string cat = cats[i].get_str();
 
         bool success;
         if (enable) {
             success = LogInstance().EnableCategory(cat);
         } else {
             success = LogInstance().DisableCategory(cat);
         }
 
         if (!success) {
             throw JSONRPCError(RPC_INVALID_PARAMETER,
                                "unknown logging category " + cat);
         }
     }
 }
 
 static UniValue logging(const Config &config, const JSONRPCRequest &request) {
     if (request.fHelp || request.params.size() > 2) {
         throw std::runtime_error(RPCHelpMan{
             "logging",
             "Gets and sets the logging configuration.\n"
             "When called without an argument, returns the list of categories "
             "with status that are currently being debug logged or not.\n"
             "When called with arguments, adds or removes categories from debug "
             "logging and return the lists above.\n"
             "The arguments are evaluated in order \"include\", \"exclude\".\n"
             "If an item is both included and excluded, it will thus end up "
             "being excluded.\n"
             "The valid logging categories are: " +
                 ListLogCategories() +
                 "\n"
                 "In addition, the following are available as category names "
                 "with special meanings:\n"
                 "  - \"all\",  \"1\" : represent all logging categories.\n"
                 "  - \"none\", \"0\" : even if other logging categories are "
                 "specified, ignore all of them.\n",
             {
                 {"include",
                  RPCArg::Type::ARR,
-                 /* opt */ true,
-                 /* default_val */ "null",
+                 RPCArg::Optional::OMITTED_NAMED_ARG,
                  "A json array of categories to add debug logging",
                  {
                      {"include_category", RPCArg::Type::STR,
-                      /* opt */ false, /* default_val */ "",
-                      "the valid logging category"},
+                      RPCArg::Optional::OMITTED, "the valid logging category"},
                  }},
                 {"exclude",
                  RPCArg::Type::ARR,
-                 /* opt */ true,
-                 /* default_val */ "null",
+                 RPCArg::Optional::OMITTED_NAMED_ARG,
                  "A json array of categories to remove debug logging",
                  {
                      {"exclude_category", RPCArg::Type::STR,
-                      /* opt */ false, /* default_val */ "",
-                      "the valid logging category"},
+                      RPCArg::Optional::OMITTED, "the valid logging category"},
                  }},
             },
             RPCResult{"{                   (json object where keys are the "
                       "logging categories, and values indicates its status\n"
                       "  \"category\": 0|1,  (numeric) if being debug logged "
                       "or not. 0:inactive, 1:active\n"
                       "  ...\n"
                       "}\n"},
             RPCExamples{HelpExampleCli("logging",
                                        "\"[\\\"all\\\"]\" \"[\\\"http\\\"]\"") +
                         HelpExampleRpc("logging", "[\"all\"], \"[libevent]\"")},
         }
                                      .ToString());
     }
 
     uint32_t original_log_categories = LogInstance().GetCategoryMask();
     if (request.params[0].isArray()) {
         EnableOrDisableLogCategories(request.params[0], true);
     }
 
     if (request.params[1].isArray()) {
         EnableOrDisableLogCategories(request.params[1], false);
     }
 
     uint32_t updated_log_categories = LogInstance().GetCategoryMask();
     uint32_t changed_log_categories =
         original_log_categories ^ updated_log_categories;
 
     /**
      * Update libevent logging if BCLog::LIBEVENT has changed.
      * If the library version doesn't allow it, UpdateHTTPServerLogging()
      * returns false, in which case we should clear the BCLog::LIBEVENT flag.
      * Throw an error if the user has explicitly asked to change only the
      * libevent flag and it failed.
      */
     if (changed_log_categories & BCLog::LIBEVENT) {
         if (!UpdateHTTPServerLogging(
                 LogInstance().WillLogCategory(BCLog::LIBEVENT))) {
             LogInstance().DisableCategory(BCLog::LIBEVENT);
             if (changed_log_categories == BCLog::LIBEVENT) {
                 throw JSONRPCError(RPC_INVALID_PARAMETER,
                                    "libevent logging cannot be updated when "
                                    "using libevent before v2.1.1.");
             }
         }
     }
 
     UniValue result(UniValue::VOBJ);
     std::vector<CLogCategoryActive> vLogCatActive = ListActiveLogCategories();
     for (const auto &logCatActive : vLogCatActive) {
         result.pushKV(logCatActive.category, logCatActive.active);
     }
 
     return result;
 }
 
 static UniValue echo(const Config &config, const JSONRPCRequest &request) {
     if (request.fHelp) {
         throw std::runtime_error(RPCHelpMan{
             "echo|echojson ...",
             "\nSimply echo back the input arguments. This command is for "
             "testing.\n"
             "\nThe difference between echo and echojson is that echojson has "
             "argument conversion enabled in the client-side table in "
             "bitcoin-cli and the GUI. There is no server-side difference.",
             {},
             RPCResults{},
             RPCExamples{""},
         }
                                      .ToString());
     }
 
     CHECK_NONFATAL(request.params.size() != 100);
 
     return request.params;
 }
 
 // clang-format off
 static const CRPCCommand commands[] = {
     //  category            name                      actor (function)        argNames
     //  ------------------- ------------------------  ----------------------  ----------
     { "control",            "getmemoryinfo",          getmemoryinfo,          {"mode"} },
     { "control",            "logging",                logging,                {"include", "exclude"} },
     { "util",               "validateaddress",        validateaddress,        {"address"} },
     { "util",               "createmultisig",         createmultisig,         {"nrequired","keys"} },
     { "util",               "deriveaddresses",        deriveaddresses,        {"descriptor", "begin", "end"} },
     { "util",               "verifymessage",          verifymessage,          {"address","signature","message"} },
     { "util",               "signmessagewithprivkey", signmessagewithprivkey, {"privkey","message"} },
     /* Not shown in help */
     { "hidden",             "setmocktime",            setmocktime,            {"timestamp"}},
     { "hidden",             "echo",                   echo,                   {"arg0","arg1","arg2","arg3","arg4","arg5","arg6","arg7","arg8","arg9"}},
     { "hidden",             "echojson",               echo,                   {"arg0","arg1","arg2","arg3","arg4","arg5","arg6","arg7","arg8","arg9"}},
 };
 // clang-format on
 
 void RegisterMiscRPCCommands(CRPCTable &t) {
     for (unsigned int vcidx = 0; vcidx < ARRAYLEN(commands); vcidx++) {
         t.appendCommand(commands[vcidx].name, &commands[vcidx]);
     }
 }
diff --git a/src/rpc/net.cpp b/src/rpc/net.cpp
index a86adcc6f..d472dfccf 100644
--- a/src/rpc/net.cpp
+++ b/src/rpc/net.cpp
@@ -1,938 +1,930 @@
 // Copyright (c) 2009-2016 The Bitcoin Core developers
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
 #include <rpc/server.h>
 
 #include <banman.h>
 #include <chainparams.h>
 #include <clientversion.h>
 #include <config.h>
 #include <core_io.h>
 #include <net.h>
 #include <net_permissions.h>
 #include <net_processing.h>
 #include <netbase.h>
 #include <policy/policy.h>
 #include <policy/settings.h>
 #include <rpc/protocol.h>
 #include <rpc/util.h>
 #include <sync.h>
 #include <timedata.h>
 #include <ui_interface.h>
 #include <util/strencodings.h>
 #include <util/system.h>
 #include <validation.h>
 #include <version.h>
 #include <warnings.h>
 
 #include <univalue.h>
 
 static UniValue getconnectioncount(const Config &config,
                                    const JSONRPCRequest &request) {
     if (request.fHelp || request.params.size() != 0) {
         throw std::runtime_error(RPCHelpMan{
             "getconnectioncount",
             "\nReturns the number of connections to other nodes.\n",
             {},
             RPCResult{"n          (numeric) The connection count\n"},
             RPCExamples{HelpExampleCli("getconnectioncount", "") +
                         HelpExampleRpc("getconnectioncount", "")},
         }
                                      .ToString());
     }
 
     if (!g_connman) {
         throw JSONRPCError(
             RPC_CLIENT_P2P_DISABLED,
             "Error: Peer-to-peer functionality missing or disabled");
     }
 
     return int(g_connman->GetNodeCount(CConnman::CONNECTIONS_ALL));
 }
 
 static UniValue ping(const Config &config, const JSONRPCRequest &request) {
     if (request.fHelp || request.params.size() != 0) {
         throw std::runtime_error(RPCHelpMan{
             "ping",
             "\nRequests that a ping be sent to all other nodes, to measure "
             "ping time.\n"
             "Results provided in getpeerinfo, pingtime and pingwait fields "
             "are decimal seconds.\n"
             "Ping command is handled in queue with all other commands, so "
             "it measures processing backlog, not just network ping.\n",
             {},
             RPCResults{},
             RPCExamples{HelpExampleCli("ping", "") +
                         HelpExampleRpc("ping", "")},
         }
                                      .ToString());
     }
 
     if (!g_connman) {
         throw JSONRPCError(
             RPC_CLIENT_P2P_DISABLED,
             "Error: Peer-to-peer functionality missing or disabled");
     }
 
     // Request that each node send a ping during next message processing pass
     g_connman->ForEachNode([](CNode *pnode) { pnode->fPingQueued = true; });
     return NullUniValue;
 }
 
 static UniValue getpeerinfo(const Config &config,
                             const JSONRPCRequest &request) {
     if (request.fHelp || request.params.size() != 0) {
         throw std::runtime_error(RPCHelpMan{
             "getpeerinfo",
             "\nReturns data about each connected network node as a json array "
             "of objects.\n",
             {},
             RPCResult{
                 "[\n"
                 "  {\n"
                 "    \"id\": n,                   (numeric) Peer index\n"
                 "    \"addr\":\"host:port\",      (string) The IP address and "
                 "port of the peer\n"
                 "    \"addrbind\":\"ip:port\",    (string) Bind address of the "
                 "connection to the peer\n"
                 "    \"addrlocal\":\"ip:port\",   (string) Local address as "
                 "reported by the peer\n"
                 "    \"services\":\"xxxxxxxxxxxxxxxx\",   (string) The "
                 "services offered\n"
                 "    \"relaytxes\":true|false,    (boolean) Whether peer has "
                 "asked us to relay transactions to it\n"
                 "    \"lastsend\": ttt,           (numeric) The time in "
                 "seconds since epoch (Jan 1 1970 GMT) of the last send\n"
                 "    \"lastrecv\": ttt,           (numeric) The time in "
                 "seconds since epoch (Jan 1 1970 GMT) of the last receive\n"
                 "    \"bytessent\": n,            (numeric) The total bytes "
                 "sent\n"
                 "    \"bytesrecv\": n,            (numeric) The total bytes "
                 "received\n"
                 "    \"conntime\": ttt,           (numeric) The connection "
                 "time in seconds since epoch (Jan 1 1970 GMT)\n"
                 "    \"timeoffset\": ttt,         (numeric) The time offset in "
                 "seconds\n"
                 "    \"pingtime\": n,             (numeric) ping time (if "
                 "available)\n"
                 "    \"minping\": n,              (numeric) minimum observed "
                 "ping time (if any at all)\n"
                 "    \"pingwait\": n,             (numeric) ping wait (if "
                 "non-zero)\n"
                 "    \"version\": v,              (numeric) The peer version, "
                 "such as 70001\n"
                 "    \"subver\": \"/Satoshi:0.8.5/\",  (string) The string "
                 "version\n"
                 "    \"inbound\": true|false,     (boolean) Inbound (true) or "
                 "Outbound (false)\n"
                 "    \"addnode\": true|false,     (boolean) Whether connection "
                 "was due to addnode/-connect or if it was an automatic/inbound "
                 "connection\n"
                 "    \"startingheight\": n,       (numeric) The starting "
                 "height (block) of the peer\n"
                 "    \"banscore\": n,             (numeric) The ban score\n"
                 "    \"synced_headers\": n,       (numeric) The last header we "
                 "have in common with this peer\n"
                 "    \"synced_blocks\": n,        (numeric) The last block we "
                 "have in common with this peer\n"
                 "    \"inflight\": [\n"
                 "       n,                        (numeric) The heights of "
                 "blocks we're currently asking from this peer\n"
                 "       ...\n"
                 "    ],\n"
                 "    \"whitelisted\": true|false, (boolean) Whether the peer "
                 "is whitelisted\n"
                 "    \"minfeefilter\": n,         (numeric) The minimum fee "
                 "rate for transactions this peer accepts\n"
                 "    \"bytessent_per_msg\": {\n"
                 "       \"addr\": n,              (numeric) The total bytes "
                 "sent aggregated by message type\n"
                 "       ...\n"
                 "    },\n"
                 "    \"bytesrecv_per_msg\": {\n"
                 "       \"addr\": n,              (numeric) The total bytes "
                 "received aggregated by message type\n"
                 "       ...\n"
                 "    }\n"
                 "  }\n"
                 "  ,...\n"
                 "]\n"},
             RPCExamples{HelpExampleCli("getpeerinfo", "") +
                         HelpExampleRpc("getpeerinfo", "")},
         }
                                      .ToString());
     }
 
     if (!g_connman) {
         throw JSONRPCError(
             RPC_CLIENT_P2P_DISABLED,
             "Error: Peer-to-peer functionality missing or disabled");
     }
 
     std::vector<CNodeStats> vstats;
     g_connman->GetNodeStats(vstats);
 
     UniValue ret(UniValue::VARR);
 
     for (const CNodeStats &stats : vstats) {
         UniValue obj(UniValue::VOBJ);
         CNodeStateStats statestats;
         bool fStateStats = GetNodeStateStats(stats.nodeid, statestats);
         obj.pushKV("id", stats.nodeid);
         obj.pushKV("addr", stats.addrName);
         if (!(stats.addrLocal.empty())) {
             obj.pushKV("addrlocal", stats.addrLocal);
         }
         if (stats.addrBind.IsValid()) {
             obj.pushKV("addrbind", stats.addrBind.ToString());
         }
         obj.pushKV("services", strprintf("%016x", stats.nServices));
         obj.pushKV("relaytxes", stats.fRelayTxes);
         obj.pushKV("lastsend", stats.nLastSend);
         obj.pushKV("lastrecv", stats.nLastRecv);
         obj.pushKV("bytessent", stats.nSendBytes);
         obj.pushKV("bytesrecv", stats.nRecvBytes);
         obj.pushKV("conntime", stats.nTimeConnected);
         obj.pushKV("timeoffset", stats.nTimeOffset);
         if (stats.dPingTime > 0.0) {
             obj.pushKV("pingtime", stats.dPingTime);
         }
         if (stats.dMinPing <
             static_cast<double>(std::numeric_limits<int64_t>::max()) / 1e6) {
             obj.pushKV("minping", stats.dMinPing);
         }
         if (stats.dPingWait > 0.0) {
             obj.pushKV("pingwait", stats.dPingWait);
         }
         obj.pushKV("version", stats.nVersion);
         // Use the sanitized form of subver here, to avoid tricksy remote peers
         // from corrupting or modifying the JSON output by putting special
         // characters in their ver message.
         obj.pushKV("subver", stats.cleanSubVer);
         obj.pushKV("inbound", stats.fInbound);
         obj.pushKV("addnode", stats.m_manual_connection);
         obj.pushKV("startingheight", stats.nStartingHeight);
         if (fStateStats) {
             obj.pushKV("banscore", statestats.nMisbehavior);
             obj.pushKV("synced_headers", statestats.nSyncHeight);
             obj.pushKV("synced_blocks", statestats.nCommonHeight);
             UniValue heights(UniValue::VARR);
             for (const int height : statestats.vHeightInFlight) {
                 heights.push_back(height);
             }
             obj.pushKV("inflight", heights);
         }
         obj.pushKV("whitelisted", stats.m_legacyWhitelisted);
         UniValue permissions(UniValue::VARR);
         for (const auto &permission :
              NetPermissions::ToStrings(stats.m_permissionFlags)) {
             permissions.push_back(permission);
         }
         obj.pushKV("permissions", permissions);
         obj.pushKV("minfeefilter", ValueFromAmount(stats.minFeeFilter));
 
         UniValue sendPerMsgCmd(UniValue::VOBJ);
         for (const mapMsgCmdSize::value_type &i : stats.mapSendBytesPerMsgCmd) {
             if (i.second > 0) {
                 sendPerMsgCmd.pushKV(i.first, i.second);
             }
         }
         obj.pushKV("bytessent_per_msg", sendPerMsgCmd);
 
         UniValue recvPerMsgCmd(UniValue::VOBJ);
         for (const mapMsgCmdSize::value_type &i : stats.mapRecvBytesPerMsgCmd) {
             if (i.second > 0) {
                 recvPerMsgCmd.pushKV(i.first, i.second);
             }
         }
         obj.pushKV("bytesrecv_per_msg", recvPerMsgCmd);
 
         ret.push_back(obj);
     }
 
     return ret;
 }
 
 static UniValue addnode(const Config &config, const JSONRPCRequest &request) {
     std::string strCommand;
     if (!request.params[1].isNull()) {
         strCommand = request.params[1].get_str();
     }
 
     if (request.fHelp || request.params.size() != 2 ||
         (strCommand != "onetry" && strCommand != "add" &&
          strCommand != "remove")) {
         throw std::runtime_error(RPCHelpMan{
             "addnode",
             "\nAttempts to add or remove a node from the addnode list.\n"
             "Or try a connection to a node once.\n"
             "Nodes added using addnode (or -connect) are protected from "
             "DoS disconnection and are not required to be\n"
             "full nodes as other outbound peers are (though such peers "
             "will not be synced from).\n",
             {
-                {"node", RPCArg::Type::STR, /* opt */ false,
-                 /* default_val */ "", "The node (see getpeerinfo for nodes)"},
-                {"command", RPCArg::Type::STR, /* opt */ false,
-                 /* default_val */ "",
+                {"node", RPCArg::Type::STR, RPCArg::Optional::NO,
+                 "The node (see getpeerinfo for nodes)"},
+                {"command", RPCArg::Type::STR, RPCArg::Optional::NO,
                  "'add' to add a node to the list, 'remove' to remove a "
                  "node from the list, 'onetry' to try a connection to the "
                  "node once"},
             },
             RPCResults{},
             RPCExamples{
                 HelpExampleCli("addnode", "\"192.168.0.6:8333\" \"onetry\"") +
                 HelpExampleRpc("addnode", "\"192.168.0.6:8333\", \"onetry\"")},
         }
                                      .ToString());
     }
 
     if (!g_connman) {
         throw JSONRPCError(
             RPC_CLIENT_P2P_DISABLED,
             "Error: Peer-to-peer functionality missing or disabled");
     }
 
     std::string strNode = request.params[0].get_str();
 
     if (strCommand == "onetry") {
         CAddress addr;
         g_connman->OpenNetworkConnection(addr, false, nullptr, strNode.c_str(),
                                          false, false, true);
         return NullUniValue;
     }
 
     if ((strCommand == "add") && (!g_connman->AddNode(strNode))) {
         throw JSONRPCError(RPC_CLIENT_NODE_ALREADY_ADDED,
                            "Error: Node already added");
     } else if ((strCommand == "remove") &&
                (!g_connman->RemoveAddedNode(strNode))) {
         throw JSONRPCError(RPC_CLIENT_NODE_NOT_ADDED,
                            "Error: Node has not been added.");
     }
 
     return NullUniValue;
 }
 
 static UniValue disconnectnode(const Config &config,
                                const JSONRPCRequest &request) {
     if (request.fHelp || request.params.size() == 0 ||
         request.params.size() >= 3) {
         throw std::runtime_error(RPCHelpMan{
             "disconnectnode",
             "\nImmediately disconnects from the specified peer node.\n"
             "\nStrictly one out of 'address' and 'nodeid' can be provided "
             "to identify the node.\n"
             "\nTo disconnect by nodeid, either set 'address' to the empty "
             "string, or call using the named 'nodeid' argument only.\n",
             {
-                {"address", RPCArg::Type::STR, /* opt */ true,
-                 /* default_val */ "fallback to nodeid",
+                {"address", RPCArg::Type::STR,
+                 /* default */ "fallback to nodeid",
                  "The IP address/port of the node"},
-                {"nodeid", RPCArg::Type::NUM, /* opt */ true,
-                 /* default_val */ "fallback to address",
+                {"nodeid", RPCArg::Type::NUM,
+                 /* default */ "fallback to address",
                  "The node ID (see getpeerinfo for node IDs)"},
             },
             RPCResults{},
             RPCExamples{
                 HelpExampleCli("disconnectnode", "\"192.168.0.6:8333\"") +
                 HelpExampleCli("disconnectnode", "\"\" 1") +
                 HelpExampleRpc("disconnectnode", "\"192.168.0.6:8333\"") +
                 HelpExampleRpc("disconnectnode", "\"\", 1")},
         }
                                      .ToString());
     }
 
     if (!g_connman) {
         throw JSONRPCError(
             RPC_CLIENT_P2P_DISABLED,
             "Error: Peer-to-peer functionality missing or disabled");
     }
 
     bool success;
     const UniValue &address_arg = request.params[0];
     const UniValue &id_arg = request.params[1];
 
     if (!address_arg.isNull() && id_arg.isNull()) {
         /* handle disconnect-by-address */
         success = g_connman->DisconnectNode(address_arg.get_str());
     } else if (!id_arg.isNull() &&
                (address_arg.isNull() ||
                 (address_arg.isStr() && address_arg.get_str().empty()))) {
         /* handle disconnect-by-id */
         NodeId nodeid = (NodeId)id_arg.get_int64();
         success = g_connman->DisconnectNode(nodeid);
     } else {
         throw JSONRPCError(
             RPC_INVALID_PARAMS,
             "Only one of address and nodeid should be provided.");
     }
 
     if (!success) {
         throw JSONRPCError(RPC_CLIENT_NODE_NOT_CONNECTED,
                            "Node not found in connected nodes");
     }
 
     return NullUniValue;
 }
 
 static UniValue getaddednodeinfo(const Config &config,
                                  const JSONRPCRequest &request) {
     if (request.fHelp || request.params.size() > 1) {
         throw std::runtime_error(RPCHelpMan{
             "getaddednodeinfo",
             "\nReturns information about the given added node, or "
             "all added nodes\n"
             "(note that onetry addnodes are not listed here)\n",
             {
-                {"node", RPCArg::Type::STR, /* opt */ true,
-                 /* default_val */ "all nodes",
+                {"node", RPCArg::Type::STR, /* default */ "all nodes",
                  "If provided, return information about this specific node, "
                  "otherwise all nodes are returned."},
             },
             RPCResult{
                 "[\n"
                 "  {\n"
                 "    \"addednode\" : \"192.168.0.201\",   (string) The node IP "
                 "address or name (as provided to addnode)\n"
                 "    \"connected\" : true|false,          (boolean) If "
                 "connected\n"
                 "    \"addresses\" : [                    (list of objects) "
                 "Only when connected = true\n"
                 "       {\n"
                 "         \"address\" : \"192.168.0.201:8333\",  (string) The "
                 "bitcoin server IP and port we're connected to\n"
                 "         \"connected\" : \"outbound\"           (string) "
                 "connection, inbound or outbound\n"
                 "       }\n"
                 "     ]\n"
                 "  }\n"
                 "  ,...\n"
                 "]\n"},
             RPCExamples{
                 HelpExampleCli("getaddednodeinfo", "\"192.168.0.201\"") +
                 HelpExampleRpc("getaddednodeinfo", "\"192.168.0.201\"")},
         }
                                      .ToString());
     }
 
     if (!g_connman) {
         throw JSONRPCError(
             RPC_CLIENT_P2P_DISABLED,
             "Error: Peer-to-peer functionality missing or disabled");
     }
 
     std::vector<AddedNodeInfo> vInfo = g_connman->GetAddedNodeInfo();
 
     if (!request.params[0].isNull()) {
         bool found = false;
         for (const AddedNodeInfo &info : vInfo) {
             if (info.strAddedNode == request.params[0].get_str()) {
                 vInfo.assign(1, info);
                 found = true;
                 break;
             }
         }
         if (!found) {
             throw JSONRPCError(RPC_CLIENT_NODE_NOT_ADDED,
                                "Error: Node has not been added.");
         }
     }
 
     UniValue ret(UniValue::VARR);
 
     for (const AddedNodeInfo &info : vInfo) {
         UniValue obj(UniValue::VOBJ);
         obj.pushKV("addednode", info.strAddedNode);
         obj.pushKV("connected", info.fConnected);
         UniValue addresses(UniValue::VARR);
         if (info.fConnected) {
             UniValue address(UniValue::VOBJ);
             address.pushKV("address", info.resolvedAddress.ToString());
             address.pushKV("connected", info.fInbound ? "inbound" : "outbound");
             addresses.push_back(address);
         }
         obj.pushKV("addresses", addresses);
         ret.push_back(obj);
     }
 
     return ret;
 }
 
 static UniValue getnettotals(const Config &config,
                              const JSONRPCRequest &request) {
     if (request.fHelp || request.params.size() > 0) {
         throw std::runtime_error(RPCHelpMan{
             "getnettotals",
             "\nReturns information about network traffic, including "
             "bytes in, bytes out,\n"
             "and current time.\n",
             {},
             RPCResult{
                 "{\n"
                 "  \"totalbytesrecv\": n,   (numeric) Total bytes received\n"
                 "  \"totalbytessent\": n,   (numeric) Total bytes sent\n"
                 "  \"timemillis\": t,       (numeric) Current UNIX time in "
                 "milliseconds\n"
                 "  \"uploadtarget\":\n"
                 "  {\n"
                 "    \"timeframe\": n,                         (numeric) "
                 "Length of the measuring timeframe in seconds\n"
                 "    \"target\": n,                            (numeric) "
                 "Target in bytes\n"
                 "    \"target_reached\": true|false,           (boolean) True "
                 "if target is reached\n"
                 "    \"serve_historical_blocks\": true|false,  (boolean) True "
                 "if serving historical blocks\n"
                 "    \"bytes_left_in_cycle\": t,               (numeric) Bytes "
                 "left in current time cycle\n"
                 "    \"time_left_in_cycle\": t                 (numeric) "
                 "Seconds left in current time cycle\n"
                 "  }\n"
                 "}\n"},
             RPCExamples{HelpExampleCli("getnettotals", "") +
                         HelpExampleRpc("getnettotals", "")},
         }
                                      .ToString());
     }
 
     if (!g_connman) {
         throw JSONRPCError(
             RPC_CLIENT_P2P_DISABLED,
             "Error: Peer-to-peer functionality missing or disabled");
     }
 
     UniValue obj(UniValue::VOBJ);
     obj.pushKV("totalbytesrecv", g_connman->GetTotalBytesRecv());
     obj.pushKV("totalbytessent", g_connman->GetTotalBytesSent());
     obj.pushKV("timemillis", GetTimeMillis());
 
     UniValue outboundLimit(UniValue::VOBJ);
     outboundLimit.pushKV("timeframe", g_connman->GetMaxOutboundTimeframe());
     outboundLimit.pushKV("target", g_connman->GetMaxOutboundTarget());
     outboundLimit.pushKV("target_reached",
                          g_connman->OutboundTargetReached(false));
     outboundLimit.pushKV("serve_historical_blocks",
                          !g_connman->OutboundTargetReached(true));
     outboundLimit.pushKV("bytes_left_in_cycle",
                          g_connman->GetOutboundTargetBytesLeft());
     outboundLimit.pushKV("time_left_in_cycle",
                          g_connman->GetMaxOutboundTimeLeftInCycle());
     obj.pushKV("uploadtarget", outboundLimit);
     return obj;
 }
 
 static UniValue GetNetworksInfo() {
     UniValue networks(UniValue::VARR);
     for (int n = 0; n < NET_MAX; ++n) {
         enum Network network = static_cast<enum Network>(n);
         if (network == NET_UNROUTABLE || network == NET_INTERNAL) {
             continue;
         }
         proxyType proxy;
         UniValue obj(UniValue::VOBJ);
         GetProxy(network, proxy);
         obj.pushKV("name", GetNetworkName(network));
         obj.pushKV("limited", !IsReachable(network));
         obj.pushKV("reachable", IsReachable(network));
         obj.pushKV("proxy", proxy.IsValid() ? proxy.proxy.ToStringIPPort()
                                             : std::string());
         obj.pushKV("proxy_randomize_credentials", proxy.randomize_credentials);
         networks.push_back(obj);
     }
     return networks;
 }
 
 static UniValue getnetworkinfo(const Config &config,
                                const JSONRPCRequest &request) {
     if (request.fHelp || request.params.size() != 0) {
         throw std::runtime_error(RPCHelpMan{
             "getnetworkinfo",
             "Returns an object containing various state info "
             "regarding P2P networking.\n",
             {},
             RPCResult{"{\n"
                       "  \"version\": xxxxx,                      (numeric) "
                       "the server version\n"
                       "  \"subversion\": \"/Satoshi:x.x.x/\",     (string) the "
                       "server subversion string\n"
                       "  \"protocolversion\": xxxxx,              (numeric) "
                       "the protocol version\n"
                       "  \"localservices\": \"xxxxxxxxxxxxxxxx\", (string) the "
                       "services we offer to the network\n"
                       "  \"localrelay\": true|false,              (bool) true "
                       "if transaction relay is requested from peers\n"
                       "  \"timeoffset\": xxxxx,                   (numeric) "
                       "the time offset\n"
                       "  \"connections\": xxxxx,                  (numeric) "
                       "the number of connections\n"
                       "  \"networkactive\": true|false,           (bool) "
                       "whether p2p networking is enabled\n"
                       "  \"networks\": [                          (array) "
                       "information per network\n"
                       "  {\n"
                       "    \"name\": \"xxx\",                     (string) "
                       "network (ipv4, ipv6 or onion)\n"
                       "    \"limited\": true|false,               (boolean) is "
                       "the network limited using -onlynet?\n"
                       "    \"reachable\": true|false,             (boolean) is "
                       "the network reachable?\n"
                       "    \"proxy\": \"host:port\"               (string) the "
                       "proxy that is used for this network, or empty if none\n"
                       "    \"proxy_randomize_credentials\": true|false,  "
                       "(string) Whether randomized credentials are used\n"
                       "  }\n"
                       "  ,...\n"
                       "  ],\n"
                       "  \"relayfee\": x.xxxxxxxx,                (numeric) "
                       "minimum relay fee for transactions in " +
                       CURRENCY_UNIT +
                       "/kB\n"
                       "  \"excessutxocharge\": x.xxxxxxxx,        (numeric) "
                       "minimum charge for excess utxos in " +
                       CURRENCY_UNIT +
                       "\n"
                       "  \"localaddresses\": [                    (array) list "
                       "of local addresses\n"
                       "  {\n"
                       "    \"address\": \"xxxx\",                 (string) "
                       "network address\n"
                       "    \"port\": xxx,                         (numeric) "
                       "network port\n"
                       "    \"score\": xxx                         (numeric) "
                       "relative score\n"
                       "  }\n"
                       "  ,...\n"
                       "  ]\n"
                       "  \"warnings\": \"...\"                    (string) any "
                       "network and blockchain warnings\n"
                       "}\n"},
             RPCExamples{HelpExampleCli("getnetworkinfo", "") +
                         HelpExampleRpc("getnetworkinfo", "")},
         }
                                      .ToString());
     }
 
     LOCK(cs_main);
     UniValue obj(UniValue::VOBJ);
     obj.pushKV("version", CLIENT_VERSION);
     obj.pushKV("subversion", userAgent(config));
     obj.pushKV("protocolversion", PROTOCOL_VERSION);
     if (g_connman) {
         obj.pushKV("localservices",
                    strprintf("%016x", g_connman->GetLocalServices()));
     }
     obj.pushKV("localrelay", fRelayTxes);
     obj.pushKV("timeoffset", GetTimeOffset());
     if (g_connman) {
         obj.pushKV("networkactive", g_connman->GetNetworkActive());
         obj.pushKV("connections",
                    int(g_connman->GetNodeCount(CConnman::CONNECTIONS_ALL)));
     }
     obj.pushKV("networks", GetNetworksInfo());
     obj.pushKV("relayfee", ValueFromAmount(::minRelayTxFee.GetFeePerK()));
     obj.pushKV("excessutxocharge",
                ValueFromAmount(config.GetExcessUTXOCharge()));
     UniValue localAddresses(UniValue::VARR);
     {
         LOCK(cs_mapLocalHost);
         for (const std::pair<const CNetAddr, LocalServiceInfo> &item :
              mapLocalHost) {
             UniValue rec(UniValue::VOBJ);
             rec.pushKV("address", item.first.ToString());
             rec.pushKV("port", item.second.nPort);
             rec.pushKV("score", item.second.nScore);
             localAddresses.push_back(rec);
         }
     }
     obj.pushKV("localaddresses", localAddresses);
     obj.pushKV("warnings", GetWarnings("statusbar"));
     return obj;
 }
 
 static UniValue setban(const Config &config, const JSONRPCRequest &request) {
     std::string strCommand;
     if (!request.params[1].isNull()) {
         strCommand = request.params[1].get_str();
     }
 
     if (request.fHelp || request.params.size() < 2 ||
         (strCommand != "add" && strCommand != "remove")) {
         throw std::runtime_error(RPCHelpMan{
             "setban",
             "\nAttempts to add or remove an IP/Subnet from the "
             "banned list.\n",
             {
-                {"subnet", RPCArg::Type::STR, /* opt */ false,
-                 /* default_val */ "",
+                {"subnet", RPCArg::Type::STR, RPCArg::Optional::NO,
                  "The IP/Subnet (see getpeerinfo for nodes IP) with an "
                  "optional netmask (default is /32 = single IP)"},
-                {"command", RPCArg::Type::STR, /* opt */ false,
-                 /* default_val */ "",
+                {"command", RPCArg::Type::STR, RPCArg::Optional::NO,
                  "'add' to add an IP/Subnet to the list, 'remove' to "
                  "remove an IP/Subnet from the list"},
-                {"bantime", RPCArg::Type::NUM, /* opt */ true,
-                 /* default_val */ "0",
+                {"bantime", RPCArg::Type::NUM, /* default */ "0",
                  "time in seconds how long (or until when if [absolute] is "
                  "set) the IP is banned (0 or empty means using the default "
                  "time of 24h which can also be overwritten by the -bantime "
                  "startup argument)"},
-                {"absolute", RPCArg::Type::BOOL, /* opt */ true,
-                 /* default_val */ "false",
+                {"absolute", RPCArg::Type::BOOL, /* default */ "false",
                  "If set, the bantime must be an absolute timestamp in seconds "
                  "since epoch (Jan 1 1970 GMT)"},
             },
             RPCResults{},
             RPCExamples{
                 HelpExampleCli("setban", "\"192.168.0.6\" \"add\" 86400") +
                 HelpExampleCli("setban", "\"192.168.0.0/24\" \"add\"") +
                 HelpExampleRpc("setban", "\"192.168.0.6\", \"add\", 86400")},
         }
                                      .ToString());
     }
     if (!g_banman) {
         throw JSONRPCError(RPC_DATABASE_ERROR,
                            "Error: Ban database not loaded");
     }
 
     CSubNet subNet;
     CNetAddr netAddr;
     bool isSubnet = false;
 
     if (request.params[0].get_str().find('/') != std::string::npos) {
         isSubnet = true;
     }
 
     if (!isSubnet) {
         CNetAddr resolved;
         LookupHost(request.params[0].get_str().c_str(), resolved, false);
         netAddr = resolved;
     } else {
         LookupSubNet(request.params[0].get_str().c_str(), subNet);
     }
 
     if (!(isSubnet ? subNet.IsValid() : netAddr.IsValid())) {
         throw JSONRPCError(RPC_CLIENT_INVALID_IP_OR_SUBNET,
                            "Error: Invalid IP/Subnet");
     }
 
     if (strCommand == "add") {
         if (isSubnet ? g_banman->IsBanned(subNet)
                      : g_banman->IsBanned(netAddr)) {
             throw JSONRPCError(RPC_CLIENT_NODE_ALREADY_ADDED,
                                "Error: IP/Subnet already banned");
         }
 
         // Use standard bantime if not specified.
         int64_t banTime = 0;
         if (!request.params[2].isNull()) {
             banTime = request.params[2].get_int64();
         }
 
         bool absolute = false;
         if (request.params[3].isTrue()) {
             absolute = true;
         }
 
         if (isSubnet) {
             g_banman->Ban(subNet, BanReasonManuallyAdded, banTime, absolute);
             if (g_connman) {
                 g_connman->DisconnectNode(subNet);
             }
         } else {
             g_banman->Ban(netAddr, BanReasonManuallyAdded, banTime, absolute);
             if (g_connman) {
                 g_connman->DisconnectNode(netAddr);
             }
         }
     } else if (strCommand == "remove") {
         if (!(isSubnet ? g_banman->Unban(subNet) : g_banman->Unban(netAddr))) {
             throw JSONRPCError(RPC_CLIENT_INVALID_IP_OR_SUBNET,
                                "Error: Unban failed. Requested address/subnet "
                                "was not previously banned.");
         }
     }
     return NullUniValue;
 }
 
 static UniValue listbanned(const Config &config,
                            const JSONRPCRequest &request) {
     if (request.fHelp || request.params.size() != 0) {
         throw std::runtime_error(RPCHelpMan{
             "listbanned",
             "\nList all banned IPs/Subnets.\n",
             {},
             RPCResults{},
             RPCExamples{HelpExampleCli("listbanned", "") +
                         HelpExampleRpc("listbanned", "")},
         }
                                      .ToString());
     }
 
     if (!g_banman) {
         throw JSONRPCError(RPC_DATABASE_ERROR,
                            "Error: Ban database not loaded");
     }
 
     banmap_t banMap;
     g_banman->GetBanned(banMap);
 
     UniValue bannedAddresses(UniValue::VARR);
     for (const auto &entry : banMap) {
         const CBanEntry &banEntry = entry.second;
         UniValue rec(UniValue::VOBJ);
         rec.pushKV("address", entry.first.ToString());
         rec.pushKV("banned_until", banEntry.nBanUntil);
         rec.pushKV("ban_created", banEntry.nCreateTime);
         rec.pushKV("ban_reason", banEntry.banReasonToString());
 
         bannedAddresses.push_back(rec);
     }
 
     return bannedAddresses;
 }
 
 static UniValue clearbanned(const Config &config,
                             const JSONRPCRequest &request) {
     if (request.fHelp || request.params.size() != 0) {
         throw std::runtime_error(RPCHelpMan{
             "clearbanned",
             "\nClear all banned IPs.\n",
             {},
             RPCResults{},
             RPCExamples{HelpExampleCli("clearbanned", "") +
                         HelpExampleRpc("clearbanned", "")},
         }
                                      .ToString());
     }
     if (!g_banman) {
         throw JSONRPCError(
             RPC_CLIENT_P2P_DISABLED,
             "Error: Peer-to-peer functionality missing or disabled");
     }
 
     g_banman->ClearBanned();
 
     return NullUniValue;
 }
 
 static UniValue setnetworkactive(const Config &config,
                                  const JSONRPCRequest &request) {
     if (request.fHelp || request.params.size() != 1) {
         throw std::runtime_error(RPCHelpMan{
             "setnetworkactive",
             "\nDisable/enable all p2p network activity.\n",
             {
-                {"state", RPCArg::Type::BOOL, /* opt */ false,
-                 /* default_val */ "",
+                {"state", RPCArg::Type::BOOL, RPCArg::Optional::NO,
                  "true to enable networking, false to disable"},
             },
             RPCResults{},
             RPCExamples{""},
         }
                                      .ToString());
     }
 
     if (!g_connman) {
         throw JSONRPCError(
             RPC_CLIENT_P2P_DISABLED,
             "Error: Peer-to-peer functionality missing or disabled");
     }
 
     g_connman->SetNetworkActive(request.params[0].get_bool());
 
     return g_connman->GetNetworkActive();
 }
 
 static UniValue getnodeaddresses(const Config &config,
                                  const JSONRPCRequest &request) {
     if (request.fHelp || request.params.size() > 1) {
         throw std::runtime_error(RPCHelpMan{
             "getnodeaddresses",
             "\nReturn known addresses which can potentially be used "
             "to find new nodes in the network\n",
             {
-                {"count", RPCArg::Type::NUM, /* opt */ true,
-                 /* default_val */ "1",
+                {"count", RPCArg::Type::NUM, /* default */ "1",
                  "How many addresses to return. Limited to the "
                  "smaller of " +
                      std::to_string(ADDRMAN_GETADDR_MAX) + " or " +
                      std::to_string(ADDRMAN_GETADDR_MAX_PCT) +
                      "% of all known addresses."},
             },
             RPCResult{"[\n"
                       "  {\n"
                       "    \"time\": ttt,                (numeric) Timestamp "
                       "in seconds since epoch (Jan 1 1970 GMT) keeping track "
                       "of when the node was last seen\n"
                       "    \"services\": n,              (numeric) The "
                       "services offered\n"
                       "    \"address\": \"host\",          (string) The "
                       "address of the node\n"
                       "    \"port\": n                   (numeric) The port of "
                       "the node\n"
                       "  }\n"
                       "  ,....\n"
                       "]\n"},
             RPCExamples{HelpExampleCli("getnodeaddresses", "8") +
                         HelpExampleRpc("getnodeaddresses", "8")},
         }
                                      .ToString());
     }
     if (!g_connman) {
         throw JSONRPCError(
             RPC_CLIENT_P2P_DISABLED,
             "Error: Peer-to-peer functionality missing or disabled");
     }
 
     int count = 1;
     if (!request.params[0].isNull()) {
         count = request.params[0].get_int();
         if (count <= 0) {
             throw JSONRPCError(RPC_INVALID_PARAMETER,
                                "Address count out of range");
         }
     }
     // returns a shuffled list of CAddress
     std::vector<CAddress> vAddr = g_connman->GetAddresses();
     UniValue ret(UniValue::VARR);
 
     int address_return_count = std::min<int>(count, vAddr.size());
     for (int i = 0; i < address_return_count; ++i) {
         UniValue obj(UniValue::VOBJ);
         const CAddress &addr = vAddr[i];
         obj.pushKV("time", int(addr.nTime));
         obj.pushKV("services", uint64_t(addr.nServices));
         obj.pushKV("address", addr.ToStringIP());
         obj.pushKV("port", addr.GetPort());
         ret.push_back(obj);
     }
     return ret;
 }
 
 // clang-format off
 static const CRPCCommand commands[] = {
     //  category            name                      actor (function)        argNames
     //  ------------------- ------------------------  ----------------------  ----------
     { "network",            "getconnectioncount",     getconnectioncount,     {} },
     { "network",            "ping",                   ping,                   {} },
     { "network",            "getpeerinfo",            getpeerinfo,            {} },
     { "network",            "addnode",                addnode,                {"node","command"} },
     { "network",            "disconnectnode",         disconnectnode,         {"address", "nodeid"} },
     { "network",            "getaddednodeinfo",       getaddednodeinfo,       {"node"} },
     { "network",            "getnettotals",           getnettotals,           {} },
     { "network",            "getnetworkinfo",         getnetworkinfo,         {} },
     { "network",            "setban",                 setban,                 {"subnet", "command", "bantime", "absolute"} },
     { "network",            "listbanned",             listbanned,             {} },
     { "network",            "clearbanned",            clearbanned,            {} },
     { "network",            "setnetworkactive",       setnetworkactive,       {"state"} },
     { "network",            "getnodeaddresses",       getnodeaddresses,       {"count"} },
 };
 // clang-format on
 
 void RegisterNetRPCCommands(CRPCTable &t) {
     for (unsigned int vcidx = 0; vcidx < ARRAYLEN(commands); vcidx++) {
         t.appendCommand(commands[vcidx].name, &commands[vcidx]);
     }
 }
diff --git a/src/rpc/rawtransaction.cpp b/src/rpc/rawtransaction.cpp
index 2062121e3..4e70035c1 100644
--- a/src/rpc/rawtransaction.cpp
+++ b/src/rpc/rawtransaction.cpp
@@ -1,1983 +1,1949 @@
 // Copyright (c) 2010 Satoshi Nakamoto
 // Copyright (c) 2009-2016 The Bitcoin Core developers
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
 #include <chain.h>
 #include <chainparams.h>
 #include <coins.h>
 #include <compat/byteswap.h>
 #include <config.h>
 #include <consensus/tx_verify.h>
 #include <consensus/validation.h>
 #include <core_io.h>
 #include <index/txindex.h>
 #include <init.h>
 #include <interfaces/chain.h>
 #include <key_io.h>
 #include <keystore.h>
 #include <merkleblock.h>
 #include <node/psbt.h>
 #include <node/transaction.h>
 #include <policy/policy.h>
 #include <primitives/transaction.h>
 #include <psbt.h>
 #include <rpc/rawtransaction_util.h>
 #include <rpc/server.h>
 #include <rpc/util.h>
 #include <script/script.h>
 #include <script/script_error.h>
 #include <script/sign.h>
 #include <script/standard.h>
 #include <txmempool.h>
 #include <uint256.h>
 #include <util/error.h>
 #include <util/strencodings.h>
 #include <validation.h>
 #include <validationinterface.h>
 
 #include <cstdint>
 
 #include <univalue.h>
 
 static void TxToJSON(const CTransaction &tx, const BlockHash &hashBlock,
                      UniValue &entry) {
     // Call into TxToUniv() in bitcoin-common to decode the transaction hex.
     //
     // Blockchain contextual information (confirmations and blocktime) is not
     // available to code in bitcoin-common, so we query them here and push the
     // data into the returned UniValue.
     TxToUniv(tx, uint256(), entry, true, RPCSerializationFlags());
 
     if (!hashBlock.IsNull()) {
         LOCK(cs_main);
 
         entry.pushKV("blockhash", hashBlock.GetHex());
         CBlockIndex *pindex = LookupBlockIndex(hashBlock);
         if (pindex) {
             if (::ChainActive().Contains(pindex)) {
                 entry.pushKV("confirmations",
                              1 + ::ChainActive().Height() - pindex->nHeight);
                 entry.pushKV("time", pindex->GetBlockTime());
                 entry.pushKV("blocktime", pindex->GetBlockTime());
             } else {
                 entry.pushKV("confirmations", 0);
             }
         }
     }
 }
 
 static UniValue getrawtransaction(const Config &config,
                                   const JSONRPCRequest &request) {
     if (request.fHelp || request.params.size() < 1 ||
         request.params.size() > 3) {
         throw std::runtime_error(RPCHelpMan{
             "getrawtransaction",
             "\nBy default this function only works for mempool "
             "transactions. When called with a blockhash\n"
             "argument, getrawtransaction will return the transaction if "
             "the specified block is available and\n"
             "the transaction is found in that block. When called without a "
             "blockhash argument, getrawtransaction\n"
             "will return the transaction if it is in the mempool, or if "
             "-txindex is enabled and the transaction\n"
             "is in a block in the blockchain.\n"
 
             "\nReturn the raw transaction data.\n"
             "\nIf verbose is 'true', returns an Object with information "
             "about 'txid'.\n"
             "If verbose is 'false' or omitted, returns a string that is "
             "serialized, hex-encoded data for 'txid'.\n",
             {
-                {"txid", RPCArg::Type::STR_HEX, /* opt */ false,
-                 /* default_val */ "", "The transaction id"},
-                {"verbose", RPCArg::Type::BOOL, /* opt */ true,
-                 /* default_val */ "false",
+                {"txid", RPCArg::Type::STR_HEX, RPCArg::Optional::NO,
+                 "The transaction id"},
+                {"verbose", RPCArg::Type::BOOL, /* default */ "false",
                  "If false, return a string, otherwise return a json "
                  "object"},
-                {"blockhash", RPCArg::Type::STR_HEX, /* opt */ true,
-                 /* default_val */ "null",
+                {"blockhash", RPCArg::Type::STR_HEX,
+                 RPCArg::Optional::OMITTED_NAMED_ARG,
                  "The block in which to look for the transaction"},
             },
             {
                 RPCResult{"if verbose is not set or set to false",
                           "\"data\"      (string) The serialized, hex-encoded "
                           "data for 'txid'\n"},
                 RPCResult{
                     "if verbose is set to true",
                     "{\n"
                     "  \"in_active_chain\": b, (bool) Whether specified block "
                     "is in the active chain or not (only present with explicit "
                     "\"blockhash\" argument)\n"
                     "  \"hex\" : \"data\",       (string) The serialized, "
                     "hex-encoded data for 'txid'\n"
                     "  \"txid\" : \"id\",        (string) The transaction id "
                     "(same as provided)\n"
                     "  \"hash\" : \"id\",        (string) The transaction hash "
                     "(differs from txid for witness transactions)\n"
                     "  \"size\" : n,             (numeric) The serialized "
                     "transaction size\n"
                     "  \"version\" : n,          (numeric) The version\n"
                     "  \"locktime\" : ttt,       (numeric) The lock time\n"
                     "  \"vin\" : [               (array of json objects)\n"
                     "     {\n"
                     "       \"txid\": \"id\",    (string) The transaction id\n"
                     "       \"vout\": n,         (numeric) \n"
                     "       \"scriptSig\": {     (json object) The script\n"
                     "         \"asm\": \"asm\",  (string) asm\n"
                     "         \"hex\": \"hex\"   (string) hex\n"
                     "       },\n"
                     "       \"sequence\": n      (numeric) The script sequence "
                     "number\n"
                     "     }\n"
                     "     ,...\n"
                     "  ],\n"
                     "  \"vout\" : [              (array of json objects)\n"
                     "     {\n"
                     "       \"value\" : x.xxx,            (numeric) The value "
                     "in " +
                         CURRENCY_UNIT +
                         "\n"
                         "       \"n\" : n,                    (numeric) index\n"
                         "       \"scriptPubKey\" : {          (json object)\n"
                         "         \"asm\" : \"asm\",          (string) the "
                         "asm\n"
                         "         \"hex\" : \"hex\",          (string) the "
                         "hex\n"
                         "         \"reqSigs\" : n,            (numeric) The "
                         "required sigs\n"
                         "         \"type\" : \"pubkeyhash\",  (string) The "
                         "type, eg 'pubkeyhash'\n"
                         "         \"addresses\" : [           (json array of "
                         "string)\n"
                         "           \"address\"        (string) bitcoin "
                         "address\n"
                         "           ,...\n"
                         "         ]\n"
                         "       }\n"
                         "     }\n"
                         "     ,...\n"
                         "  ],\n"
                         "  \"blockhash\" : \"hash\",   (string) the block "
                         "hash\n"
                         "  \"confirmations\" : n,      (numeric) The "
                         "confirmations\n"
                         "  \"time\" : ttt,             (numeric) The "
                         "transaction time in seconds since epoch (Jan 1 1970 "
                         "GMT)\n"
                         "  \"blocktime\" : ttt         (numeric) The block "
                         "time in seconds since epoch (Jan 1 1970 GMT)\n"
                         "}\n"},
             },
             RPCExamples{
                 HelpExampleCli("getrawtransaction", "\"mytxid\"") +
                 HelpExampleCli("getrawtransaction", "\"mytxid\" true") +
                 HelpExampleRpc("getrawtransaction", "\"mytxid\", true") +
                 HelpExampleCli("getrawtransaction",
                                "\"mytxid\" false \"myblockhash\"") +
                 HelpExampleCli("getrawtransaction",
                                "\"mytxid\" true \"myblockhash\"")},
         }
                                      .ToString());
     }
 
     bool in_active_chain = true;
     TxId txid = TxId(ParseHashV(request.params[0], "parameter 1"));
     CBlockIndex *blockindex = nullptr;
 
     const CChainParams &params = config.GetChainParams();
     if (txid == params.GenesisBlock().hashMerkleRoot) {
         // Special exception for the genesis block coinbase transaction
         throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY,
                            "The genesis block coinbase is not considered an "
                            "ordinary transaction and cannot be retrieved");
     }
 
     // Accept either a bool (true) or a num (>=1) to indicate verbose output.
     bool fVerbose = false;
     if (!request.params[1].isNull()) {
         fVerbose = request.params[1].isNum()
                        ? (request.params[1].get_int() != 0)
                        : request.params[1].get_bool();
     }
 
     if (!request.params[2].isNull()) {
         LOCK(cs_main);
 
         BlockHash blockhash(ParseHashV(request.params[2], "parameter 3"));
         blockindex = LookupBlockIndex(blockhash);
         if (!blockindex) {
             throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY,
                                "Block hash not found");
         }
         in_active_chain = ::ChainActive().Contains(blockindex);
     }
 
     bool f_txindex_ready = false;
     if (g_txindex && !blockindex) {
         f_txindex_ready = g_txindex->BlockUntilSyncedToCurrentChain();
     }
 
     CTransactionRef tx;
     BlockHash hash_block;
     if (!GetTransaction(txid, tx, params.GetConsensus(), hash_block,
                         blockindex)) {
         std::string errmsg;
         if (blockindex) {
             if (!blockindex->nStatus.hasData()) {
                 throw JSONRPCError(RPC_MISC_ERROR, "Block not available");
             }
             errmsg = "No such transaction found in the provided block";
         } else if (!g_txindex) {
             errmsg = "No such mempool transaction. Use -txindex to enable "
                      "blockchain transaction queries";
         } else if (!f_txindex_ready) {
             errmsg = "No such mempool transaction. Blockchain transactions are "
                      "still in the process of being indexed";
         } else {
             errmsg = "No such mempool or blockchain transaction";
         }
         throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY,
                            errmsg +
                                ". Use gettransaction for wallet transactions.");
     }
 
     if (!fVerbose) {
         return EncodeHexTx(*tx, RPCSerializationFlags());
     }
 
     UniValue result(UniValue::VOBJ);
     if (blockindex) {
         result.pushKV("in_active_chain", in_active_chain);
     }
     TxToJSON(*tx, hash_block, result);
     return result;
 }
 
 static UniValue gettxoutproof(const Config &config,
                               const JSONRPCRequest &request) {
     if (request.fHelp ||
         (request.params.size() != 1 && request.params.size() != 2)) {
         throw std::runtime_error(RPCHelpMan{
             "gettxoutproof",
             "\nReturns a hex-encoded proof that \"txid\" was "
             "included in a block.\n"
             "\nNOTE: By default this function only works sometimes. "
             "This is when there is an\n"
             "unspent output in the utxo for this transaction. To "
             "make it always work,\n"
             "you need to maintain a transaction index, using the "
             "-txindex command line option or\n"
             "specify the block in which the transaction is included "
             "manually (by blockhash).\n",
             {
                 {
                     "txids",
                     RPCArg::Type::ARR,
-                    /* opt */ false,
-                    /* default_val */ "",
+                    RPCArg::Optional::NO,
                     "A json array of txids to filter",
                     {
-                        {"txid", RPCArg::Type::STR_HEX, /* opt */ false,
-                         /* default_val */ "", "A transaction hash"},
+                        {"txid", RPCArg::Type::STR_HEX,
+                         RPCArg::Optional::OMITTED, "A transaction hash"},
                     },
                 },
-                {"blockhash", RPCArg::Type::STR_HEX, /* opt */ true,
-                 /* default_val */ "null",
+                {"blockhash", RPCArg::Type::STR_HEX,
+                 RPCArg::Optional::OMITTED_NAMED_ARG,
                  "If specified, looks for txid in the block with this hash"},
             },
             RPCResult{"\"data\"           (string) A string that is a "
                       "serialized, hex-encoded data for the proof.\n"},
             RPCExamples{""},
         }
                                      .ToString());
     }
 
     std::set<TxId> setTxIds;
     TxId oneTxId;
     UniValue txids = request.params[0].get_array();
     for (unsigned int idx = 0; idx < txids.size(); idx++) {
         const UniValue &utxid = txids[idx];
         TxId txid(ParseHashV(utxid, "txid"));
         if (setTxIds.count(txid)) {
             throw JSONRPCError(
                 RPC_INVALID_PARAMETER,
                 std::string("Invalid parameter, duplicated txid: ") +
                     utxid.get_str());
         }
 
         setTxIds.insert(txid);
         oneTxId = txid;
     }
 
     CBlockIndex *pblockindex = nullptr;
 
     BlockHash hashBlock;
     if (!request.params[1].isNull()) {
         LOCK(cs_main);
         hashBlock = BlockHash(ParseHashV(request.params[1], "blockhash"));
         pblockindex = LookupBlockIndex(hashBlock);
         if (!pblockindex) {
             throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Block not found");
         }
     } else {
         LOCK(cs_main);
         // Loop through txids and try to find which block they're in. Exit loop
         // once a block is found.
         for (const auto &txid : setTxIds) {
             const Coin &coin = AccessByTxid(*pcoinsTip, txid);
             if (!coin.IsSpent()) {
                 pblockindex = ::ChainActive()[coin.GetHeight()];
                 break;
             }
         }
     }
 
     // Allow txindex to catch up if we need to query it and before we acquire
     // cs_main.
     if (g_txindex && !pblockindex) {
         g_txindex->BlockUntilSyncedToCurrentChain();
     }
 
     const Consensus::Params &params = config.GetChainParams().GetConsensus();
 
     LOCK(cs_main);
 
     if (pblockindex == nullptr) {
         CTransactionRef tx;
         if (!GetTransaction(oneTxId, tx, params, hashBlock) ||
             hashBlock.IsNull()) {
             throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY,
                                "Transaction not yet in block");
         }
 
         pblockindex = LookupBlockIndex(hashBlock);
         if (!pblockindex) {
             throw JSONRPCError(RPC_INTERNAL_ERROR, "Transaction index corrupt");
         }
     }
 
     CBlock block;
     if (!ReadBlockFromDisk(block, pblockindex, params)) {
         throw JSONRPCError(RPC_INTERNAL_ERROR, "Can't read block from disk");
     }
 
     unsigned int ntxFound = 0;
     for (const auto &tx : block.vtx) {
         if (setTxIds.count(tx->GetId())) {
             ntxFound++;
         }
     }
 
     if (ntxFound != setTxIds.size()) {
         throw JSONRPCError(
             RPC_INVALID_ADDRESS_OR_KEY,
             "Not all transactions found in specified or retrieved block");
     }
 
     CDataStream ssMB(SER_NETWORK, PROTOCOL_VERSION);
     CMerkleBlock mb(block, setTxIds);
     ssMB << mb;
     std::string strHex = HexStr(ssMB.begin(), ssMB.end());
     return strHex;
 }
 
 static UniValue verifytxoutproof(const Config &config,
                                  const JSONRPCRequest &request) {
     if (request.fHelp || request.params.size() != 1) {
         throw std::runtime_error(RPCHelpMan{
             "verifytxoutproof",
             "\nVerifies that a proof points to a transaction in a "
             "block, returning the transaction it commits to\n"
             "and throwing an RPC error if the block is not in our "
             "best chain\n",
             {
-                {"proof", RPCArg::Type::STR_HEX, /* opt */ false,
-                 /* default_val */ "",
+                {"proof", RPCArg::Type::STR_HEX, RPCArg::Optional::NO,
                  "The hex-encoded proof generated by gettxoutproof"},
             },
             RPCResult{"[\"txid\"]      (array, strings) The txid(s) which the "
                       "proof commits to, or empty array if the proof can not "
                       "be validated.\n"},
             RPCExamples{""},
         }
                                      .ToString());
     }
 
     CDataStream ssMB(ParseHexV(request.params[0], "proof"), SER_NETWORK,
                      PROTOCOL_VERSION);
     CMerkleBlock merkleBlock;
     ssMB >> merkleBlock;
 
     UniValue res(UniValue::VARR);
 
     std::vector<uint256> vMatch;
     std::vector<size_t> vIndex;
     if (merkleBlock.txn.ExtractMatches(vMatch, vIndex) !=
         merkleBlock.header.hashMerkleRoot) {
         return res;
     }
 
     LOCK(cs_main);
 
     const CBlockIndex *pindex = LookupBlockIndex(merkleBlock.header.GetHash());
     if (!pindex || !::ChainActive().Contains(pindex) || pindex->nTx == 0) {
         throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY,
                            "Block not found in chain");
     }
 
     // Check if proof is valid, only add results if so
     if (pindex->nTx == merkleBlock.txn.GetNumTransactions()) {
         for (const uint256 &hash : vMatch) {
             res.push_back(hash.GetHex());
         }
     }
 
     return res;
 }
 
 static UniValue createrawtransaction(const Config &config,
                                      const JSONRPCRequest &request) {
     if (request.fHelp || request.params.size() < 2 ||
         request.params.size() > 3) {
         throw std::runtime_error(RPCHelpMan{
             "createrawtransaction",
             "\nCreate a transaction spending the given inputs and creating "
             "new outputs.\n"
             "Outputs can be addresses or data.\n"
             "Returns hex-encoded raw transaction.\n"
             "Note that the transaction's inputs are not signed, and\n"
             "it is not stored in the wallet or transmitted to the network.\n",
             {
                 {
                     "inputs",
                     RPCArg::Type::ARR,
-                    /* opt */ false,
-                    /* default_val */ "",
+                    RPCArg::Optional::NO,
                     "A json array of json objects",
                     {
                         {
                             "",
                             RPCArg::Type::OBJ,
-                            /* opt */ true,
-                            /* default_val */ "",
+                            RPCArg::Optional::OMITTED,
                             "",
                             {
                                 {"txid", RPCArg::Type::STR_HEX,
-                                 /* opt */ false, /* default_val */ "",
-                                 "The transaction id"},
-                                {"vout", RPCArg::Type::NUM, /* opt */ false,
-                                 /* default_val */ "", "The output number"},
-                                {"sequence", RPCArg::Type::NUM, /* opt */ true,
-                                 /* default_val */
+                                 RPCArg::Optional::NO, "The transaction id"},
+                                {"vout", RPCArg::Type::NUM,
+                                 RPCArg::Optional::NO, "The output number"},
+                                {"sequence", RPCArg::Type::NUM, /* default */
                                  "depends on the value of the 'locktime' "
                                  "argument",
                                  "The sequence number"},
                             },
                         },
                     },
                 },
                 {
                     "outputs",
                     RPCArg::Type::ARR,
-                    /* opt */ false,
-                    /* default_val */ "",
+                    RPCArg::Optional::NO,
                     "a json array with outputs (key-value pairs).\n"
                     "For compatibility reasons, a dictionary, which holds "
                     "the key-value pairs directly, is also\n"
                     "                             accepted as second "
                     "parameter.",
                     {
                         {
                             "",
                             RPCArg::Type::OBJ,
-                            /* opt */ true,
-                            /* default_val */ "",
+                            RPCArg::Optional::OMITTED,
                             "",
                             {
                                 {"address", RPCArg::Type::AMOUNT,
-                                 /* opt */ false, /* default_val */ "",
+                                 RPCArg::Optional::NO,
                                  "A key-value pair. The key (string) is "
                                  "the bitcoin address, the value (float or "
                                  "string) is the amount in " +
                                      CURRENCY_UNIT},
                             },
                         },
                         {
                             "",
                             RPCArg::Type::OBJ,
-                            /* opt */ true,
-                            /* default_val */ "",
+                            RPCArg::Optional::OMITTED,
                             "",
                             {
                                 {"data", RPCArg::Type::STR_HEX,
-                                 /* opt */ false, /* default_val */ "",
+                                 RPCArg::Optional::NO,
                                  "A key-value pair. The key must be "
                                  "\"data\", the value is hex-encoded data"},
                             },
                         },
                     },
                 },
-                {"locktime", RPCArg::Type::NUM, /* opt */ true,
-                 /* default_val */ "0",
+                {"locktime", RPCArg::Type::NUM, /* default */ "0",
                  "Raw locktime. Non-0 value also locktime-activates "
                  "inputs"},
             },
             RPCResult{"\"transaction\"              (string) hex string of the "
                       "transaction\n"},
             RPCExamples{
                 HelpExampleCli("createrawtransaction",
                                "\"[{\\\"txid\\\":\\\"myid\\\",\\\"vout\\\":0}]"
                                "\" \"[{\\\"address\\\":0.01}]\"") +
                 HelpExampleCli("createrawtransaction",
                                "\"[{\\\"txid\\\":\\\"myid\\\",\\\"vout\\\":0}]"
                                "\" \"[{\\\"data\\\":\\\"00010203\\\"}]\"") +
                 HelpExampleRpc("createrawtransaction",
                                "\"[{\\\"txid\\\":\\\"myid\\\",\\\"vout\\\":0}]"
                                "\", \"[{\\\"address\\\":0.01}]\"") +
                 HelpExampleRpc("createrawtransaction",
                                "\"[{\\\"txid\\\":\\\"myid\\\",\\\"vout\\\":0}]"
                                "\", \"[{\\\"data\\\":\\\"00010203\\\"}]\"")},
         }
                                      .ToString());
     }
 
     RPCTypeCheck(request.params,
                  {UniValue::VARR,
                   UniValueType(), // ARR or OBJ, checked later
                   UniValue::VNUM},
                  true);
 
     CMutableTransaction rawTx =
         ConstructTransaction(config.GetChainParams(), request.params[0],
                              request.params[1], request.params[2]);
 
     return EncodeHexTx(CTransaction(rawTx));
 }
 
 static UniValue decoderawtransaction(const Config &config,
                                      const JSONRPCRequest &request) {
     if (request.fHelp || request.params.size() != 1) {
         throw std::runtime_error(RPCHelpMan{
             "decoderawtransaction",
             "\nReturn a JSON object representing the serialized, "
             "hex-encoded transaction.\n",
             {
-                {"hexstring", RPCArg::Type::STR_HEX, /* opt */ false,
-                 /* default_val */ "", "The transaction hex string"},
+                {"hexstring", RPCArg::Type::STR_HEX, RPCArg::Optional::NO,
+                 "The transaction hex string"},
             },
             RPCResult{
                 "{\n"
                 "  \"txid\" : \"id\",        (string) The transaction id\n"
                 "  \"hash\" : \"id\",        (string) The transaction hash "
                 "(differs from txid for witness transactions)\n"
                 "  \"size\" : n,             (numeric) The transaction size\n"
                 "  \"version\" : n,          (numeric) The version\n"
                 "  \"locktime\" : ttt,       (numeric) The lock time\n"
                 "  \"vin\" : [               (array of json objects)\n"
                 "     {\n"
                 "       \"txid\": \"id\",    (string) The transaction id\n"
                 "       \"vout\": n,         (numeric) The output number\n"
                 "       \"scriptSig\": {     (json object) The script\n"
                 "         \"asm\": \"asm\",  (string) asm\n"
                 "         \"hex\": \"hex\"   (string) hex\n"
                 "       },\n"
                 "       \"sequence\": n     (numeric) The script sequence "
                 "number\n"
                 "     }\n"
                 "     ,...\n"
                 "  ],\n"
                 "  \"vout\" : [             (array of json objects)\n"
                 "     {\n"
                 "       \"value\" : x.xxx,            (numeric) The value in " +
                 CURRENCY_UNIT +
                 "\n"
                 "       \"n\" : n,                    (numeric) index\n"
                 "       \"scriptPubKey\" : {          (json object)\n"
                 "         \"asm\" : \"asm\",          (string) the asm\n"
                 "         \"hex\" : \"hex\",          (string) the hex\n"
                 "         \"reqSigs\" : n,            (numeric) The required "
                 "sigs\n"
                 "         \"type\" : \"pubkeyhash\",  (string) The type, eg "
                 "'pubkeyhash'\n"
                 "         \"addresses\" : [           (json array of string)\n"
                 "           \"12tvKAXCxZjSmdNbao16dKXC8tRWfcF5oc\"   (string) "
                 "bitcoin address\n"
                 "           ,...\n"
                 "         ]\n"
                 "       }\n"
                 "     }\n"
                 "     ,...\n"
                 "  ],\n"
                 "}\n"},
             RPCExamples{
                 HelpExampleCli("decoderawtransaction", "\"hexstring\"") +
                 HelpExampleRpc("decoderawtransaction", "\"hexstring\"")},
         }
                                      .ToString());
     }
 
     RPCTypeCheck(request.params, {UniValue::VSTR});
 
     CMutableTransaction mtx;
 
     if (!DecodeHexTx(mtx, request.params[0].get_str())) {
         throw JSONRPCError(RPC_DESERIALIZATION_ERROR, "TX decode failed");
     }
 
     UniValue result(UniValue::VOBJ);
     TxToUniv(CTransaction(std::move(mtx)), uint256(), result, false);
 
     return result;
 }
 
 static UniValue decodescript(const Config &config,
                              const JSONRPCRequest &request) {
     if (request.fHelp || request.params.size() != 1) {
         throw std::runtime_error(RPCHelpMan{
             "decodescript",
             "\nDecode a hex-encoded script.\n",
             {
-                {"hexstring", RPCArg::Type::STR_HEX, /* opt */ false,
-                 /* default_val */ "", "the hex-encoded script"},
+                {"hexstring", RPCArg::Type::STR_HEX, RPCArg::Optional::NO,
+                 "the hex-encoded script"},
             },
             RPCResult{"{\n"
                       "  \"asm\":\"asm\",   (string) Script public key\n"
                       "  \"hex\":\"hex\",   (string) hex-encoded public key\n"
                       "  \"type\":\"type\", (string) The output type\n"
                       "  \"reqSigs\": n,    (numeric) The required signatures\n"
                       "  \"addresses\": [   (json array of string)\n"
                       "     \"address\"     (string) bitcoin address\n"
                       "     ,...\n"
                       "  ],\n"
                       "  \"p2sh\",\"address\" (string) address of P2SH script "
                       "wrapping this redeem script (not returned if the script "
                       "is already a P2SH).\n"
                       "}\n"},
             RPCExamples{HelpExampleCli("decodescript", "\"hexstring\"") +
                         HelpExampleRpc("decodescript", "\"hexstring\"")},
         }
                                      .ToString());
     }
 
     RPCTypeCheck(request.params, {UniValue::VSTR});
 
     UniValue r(UniValue::VOBJ);
     CScript script;
     if (request.params[0].get_str().size() > 0) {
         std::vector<uint8_t> scriptData(
             ParseHexV(request.params[0], "argument"));
         script = CScript(scriptData.begin(), scriptData.end());
     } else {
         // Empty scripts are valid.
     }
 
     ScriptPubKeyToUniv(script, r, false);
 
     UniValue type;
     type = find_value(r, "type");
 
     if (type.isStr() && type.get_str() != "scripthash") {
         // P2SH cannot be wrapped in a P2SH. If this script is already a P2SH,
         // don't return the address for a P2SH of the P2SH.
         r.pushKV("p2sh", EncodeDestination(CScriptID(script), config));
     }
 
     return r;
 }
 
 static UniValue combinerawtransaction(const Config &config,
                                       const JSONRPCRequest &request) {
     if (request.fHelp || request.params.size() != 1) {
         throw std::runtime_error(RPCHelpMan{
             "combinerawtransaction",
             "\nCombine multiple partially signed transactions into one "
             "transaction.\n"
             "The combined transaction may be another partially signed "
             "transaction or a \n"
             "fully signed transaction.",
             {
                 {
                     "txs",
                     RPCArg::Type::ARR,
-                    /* opt */ false,
-                    /* default_val */ "",
+                    RPCArg::Optional::NO,
                     "A json array of hex strings of partially signed "
                     "transactions",
                     {
                         {"hexstring", RPCArg::Type::STR_HEX,
-                         /* opt */ false, /* default_val */ "",
-                         "A transaction hash"},
+                         RPCArg::Optional::OMITTED, "A transaction hash"},
                     },
                 },
             },
             RPCResult{"\"hex\"            (string) The hex-encoded raw "
                       "transaction with signature(s)\n"},
             RPCExamples{HelpExampleCli("combinerawtransaction",
                                        "[\"myhex1\", \"myhex2\", \"myhex3\"]")},
         }
                                      .ToString());
     }
 
     UniValue txs = request.params[0].get_array();
     std::vector<CMutableTransaction> txVariants(txs.size());
 
     for (unsigned int idx = 0; idx < txs.size(); idx++) {
         if (!DecodeHexTx(txVariants[idx], txs[idx].get_str())) {
             throw JSONRPCError(RPC_DESERIALIZATION_ERROR,
                                strprintf("TX decode failed for tx %d", idx));
         }
     }
 
     if (txVariants.empty()) {
         throw JSONRPCError(RPC_DESERIALIZATION_ERROR, "Missing transactions");
     }
 
     // mergedTx will end up with all the signatures; it
     // starts as a clone of the rawtx:
     CMutableTransaction mergedTx(txVariants[0]);
 
     // Fetch previous transactions (inputs):
     CCoinsView viewDummy;
     CCoinsViewCache view(&viewDummy);
     {
         LOCK(cs_main);
         LOCK(g_mempool.cs);
         CCoinsViewCache &viewChain = *pcoinsTip;
         CCoinsViewMemPool viewMempool(&viewChain, g_mempool);
         // temporarily switch cache backend to db+mempool view
         view.SetBackend(viewMempool);
 
         for (const CTxIn &txin : mergedTx.vin) {
             // Load entries from viewChain into view; can fail.
             view.AccessCoin(txin.prevout);
         }
 
         // switch back to avoid locking mempool for too long
         view.SetBackend(viewDummy);
     }
 
     // Use CTransaction for the constant parts of the
     // transaction to avoid rehashing.
     const CTransaction txConst(mergedTx);
     // Sign what we can:
     for (size_t i = 0; i < mergedTx.vin.size(); i++) {
         CTxIn &txin = mergedTx.vin[i];
         const Coin &coin = view.AccessCoin(txin.prevout);
         if (coin.IsSpent()) {
             throw JSONRPCError(RPC_VERIFY_ERROR,
                                "Input not found or already spent");
         }
         SignatureData sigdata;
 
         const CTxOut &txout = coin.GetTxOut();
 
         // ... and merge in other signatures:
         for (const CMutableTransaction &txv : txVariants) {
             if (txv.vin.size() > i) {
                 sigdata.MergeSignatureData(DataFromTransaction(txv, i, txout));
             }
         }
         ProduceSignature(
             DUMMY_SIGNING_PROVIDER,
             MutableTransactionSignatureCreator(&mergedTx, i, txout.nValue),
             txout.scriptPubKey, sigdata);
 
         UpdateInput(txin, sigdata);
     }
 
     return EncodeHexTx(CTransaction(mergedTx));
 }
 
 static UniValue signrawtransactionwithkey(const Config &config,
                                           const JSONRPCRequest &request) {
     if (request.fHelp || request.params.size() < 2 ||
         request.params.size() > 4) {
         throw std::runtime_error(RPCHelpMan{
             "signrawtransactionwithkey",
             "\nSign inputs for raw transaction (serialized, hex-encoded).\n"
             "The second argument is an array of base58-encoded private\n"
             "keys that will be the only keys used to sign the transaction.\n"
             "The third optional argument (may be null) is an array of previous "
             "transaction outputs that\n"
             "this transaction depends on but may not yet be in the block "
             "chain.\n",
             {
-                {"hexstring", RPCArg::Type::STR_HEX, /* opt */ false,
-                 /* default_val */ "", "The transaction hex string"},
+                {"hexstring", RPCArg::Type::STR_HEX, RPCArg::Optional::NO,
+                 "The transaction hex string"},
                 {
                     "privkeys",
                     RPCArg::Type::ARR,
-                    /* opt */ false,
-                    /* default_val */ "",
+                    RPCArg::Optional::NO,
                     "A json array of base58-encoded private keys for signing",
                     {
                         {"privatekey", RPCArg::Type::STR,
-                         /* opt */ false, /* default_val */ "",
+                         RPCArg::Optional::OMITTED,
                          "private key in base58-encoding"},
                     },
                 },
                 {
                     "prevtxs",
                     RPCArg::Type::ARR,
-                    /* opt */ true,
-                    /* default_val */ "null",
+                    RPCArg::Optional::OMITTED_NAMED_ARG,
                     "A json array of previous dependent transaction outputs",
                     {
                         {
                             "",
                             RPCArg::Type::OBJ,
-                            /* opt */ true,
-                            /* default_val */ "",
+                            RPCArg::Optional::OMITTED,
                             "",
                             {
                                 {"txid", RPCArg::Type::STR_HEX,
-                                 /* opt */ false, /* default_val */ "",
-                                 "The transaction id"},
-                                {"vout", RPCArg::Type::NUM, /* opt */ false,
-                                 /* default_val */ "", "The output number"},
+                                 RPCArg::Optional::NO, "The transaction id"},
+                                {"vout", RPCArg::Type::NUM,
+                                 RPCArg::Optional::NO, "The output number"},
                                 {"scriptPubKey", RPCArg::Type::STR_HEX,
-                                 /* opt */ false, /* default_val */ "",
-                                 "script key"},
+                                 RPCArg::Optional::NO, "script key"},
                                 {"redeemScript", RPCArg::Type::STR_HEX,
-                                 /* opt */ true, /* default_val */ "omitted",
+                                 RPCArg::Optional::OMITTED,
                                  "(required for P2SH) redeem script"},
                                 {"amount", RPCArg::Type::AMOUNT,
-                                 /* opt */ false, /* default_val */ "",
-                                 "The amount spent"},
+                                 RPCArg::Optional::NO, "The amount spent"},
                             },
                         },
                     },
                 },
-                {"sighashtype", RPCArg::Type::STR, /* opt */ true,
-                 /* default_val */ "ALL|FORKID",
+                {"sighashtype", RPCArg::Type::STR, /* default */ "ALL|FORKID",
                  "The signature hash type. Must be one of:\n"
                  "       \"ALL|FORKID\"\n"
                  "       \"NONE|FORKID\"\n"
                  "       \"SINGLE|FORKID\"\n"
                  "       \"ALL|FORKID|ANYONECANPAY\"\n"
                  "       \"NONE|FORKID|ANYONECANPAY\"\n"
                  "       \"SINGLE|FORKID|ANYONECANPAY\""},
             },
             RPCResult{"{\n"
                       "  \"hex\" : \"value\",                  (string) The "
                       "hex-encoded raw transaction with signature(s)\n"
                       "  \"complete\" : true|false,          (boolean) If the "
                       "transaction has a complete set of signatures\n"
                       "  \"errors\" : [                      (json array of "
                       "objects) Script verification errors (if there are any)\n"
                       "    {\n"
                       "      \"txid\" : \"hash\",              (string) The "
                       "hash of the referenced, previous transaction\n"
                       "      \"vout\" : n,                   (numeric) The "
                       "index of the output to spent and used as input\n"
                       "      \"scriptSig\" : \"hex\",          (string) The "
                       "hex-encoded signature script\n"
                       "      \"sequence\" : n,               (numeric) Script "
                       "sequence number\n"
                       "      \"error\" : \"text\"              (string) "
                       "Verification or signing error related to the input\n"
                       "    }\n"
                       "    ,...\n"
                       "  ]\n"
                       "}\n"},
             RPCExamples{
                 HelpExampleCli("signrawtransactionwithkey", "\"myhex\"") +
                 HelpExampleRpc("signrawtransactionwithkey", "\"myhex\"")},
         }
                                      .ToString());
     }
 
     RPCTypeCheck(
         request.params,
         {UniValue::VSTR, UniValue::VARR, UniValue::VARR, UniValue::VSTR}, true);
 
     CMutableTransaction mtx;
     if (!DecodeHexTx(mtx, request.params[0].get_str())) {
         throw JSONRPCError(RPC_DESERIALIZATION_ERROR, "TX decode failed");
     }
 
     CBasicKeyStore keystore;
     const UniValue &keys = request.params[1].get_array();
     for (size_t idx = 0; idx < keys.size(); ++idx) {
         UniValue k = keys[idx];
         CKey key = DecodeSecret(k.get_str());
         if (!key.IsValid()) {
             throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY,
                                "Invalid private key");
         }
         keystore.AddKey(key);
     }
 
     return SignTransaction(*g_rpc_node->chain, mtx, request.params[2],
                            &keystore, true, request.params[3]);
 }
 
 static UniValue sendrawtransaction(const Config &config,
                                    const JSONRPCRequest &request) {
     if (request.fHelp || request.params.size() < 1 ||
         request.params.size() > 2) {
         throw std::runtime_error(RPCHelpMan{
             "sendrawtransaction",
             "\nSubmits raw transaction (serialized, hex-encoded) to local node "
             "and network.\n"
             "\nAlso see createrawtransaction and "
             "signrawtransactionwithkey calls.\n",
             {
-                {"hexstring", RPCArg::Type::STR_HEX, /* opt */ false,
-                 /* default_val */ "", "The hex string of the raw transaction"},
-                {"allowhighfees", RPCArg::Type::BOOL, /* opt */ true,
-                 /* default_val */ "false", "Allow high fees"},
+                {"hexstring", RPCArg::Type::STR_HEX, RPCArg::Optional::NO,
+                 "The hex string of the raw transaction"},
+                {"allowhighfees", RPCArg::Type::BOOL, /* default */ "false",
+                 "Allow high fees"},
             },
             RPCResult{
                 "\"hex\"             (string) The transaction hash in hex\n"},
             RPCExamples{
                 "\nCreate a transaction\n" +
                 HelpExampleCli(
                     "createrawtransaction",
                     "\"[{\\\"txid\\\" : \\\"mytxid\\\",\\\"vout\\\":0}]\" "
                     "\"{\\\"myaddress\\\":0.01}\"") +
                 "Sign the transaction, and get back the hex\n" +
                 HelpExampleCli("signrawtransactionwithwallet", "\"myhex\"") +
                 "\nSend the transaction (signed hex)\n" +
                 HelpExampleCli("sendrawtransaction", "\"signedhex\"") +
                 "\nAs a JSON-RPC call\n" +
                 HelpExampleRpc("sendrawtransaction", "\"signedhex\"")},
         }
                                      .ToString());
     }
 
     RPCTypeCheck(request.params, {UniValue::VSTR, UniValue::VBOOL});
 
     // parse hex string from parameter
     CMutableTransaction mtx;
     if (!DecodeHexTx(mtx, request.params[0].get_str())) {
         throw JSONRPCError(RPC_DESERIALIZATION_ERROR, "TX decode failed");
     }
 
     CTransactionRef tx(MakeTransactionRef(std::move(mtx)));
 
     bool allowhighfees = false;
     if (!request.params[1].isNull()) {
         allowhighfees = request.params[1].get_bool();
     }
     const Amount highfee{allowhighfees ? Amount::zero() : ::maxTxFee};
     TxId txid;
     std::string err_string;
     const TransactionError err =
         BroadcastTransaction(config, tx, txid, err_string, highfee);
     if (err != TransactionError::OK) {
         throw JSONRPCTransactionError(err, err_string);
     }
 
     return txid.GetHex();
 }
 
 static UniValue testmempoolaccept(const Config &config,
                                   const JSONRPCRequest &request) {
     if (request.fHelp || request.params.size() < 1 ||
         request.params.size() > 2) {
         throw std::runtime_error(RPCHelpMan{
             "testmempoolaccept",
             "\nReturns if raw transaction (serialized, hex-encoded) would be "
             "accepted by mempool.\n"
             "\nThis checks if the transaction violates the consensus or policy "
             "rules.\n"
             "\nSee sendrawtransaction call.\n",
             {
                 {
                     "rawtxs",
                     RPCArg::Type::ARR,
-                    /* opt */ false,
-                    /* default_val */ "",
+                    RPCArg::Optional::NO,
                     "An array of hex strings of raw transactions.\n"
                     "                                        Length must be "
                     "one for now.",
                     {
                         {"rawtx", RPCArg::Type::STR_HEX,
-                         /* opt */ false, /* default_val */ "", ""},
+                         RPCArg::Optional::OMITTED, ""},
                     },
                 },
-                {"allowhighfees", RPCArg::Type::BOOL, /* opt */ true,
-                 /* default_val */ "false", "Allow high fees"},
+                {"allowhighfees", RPCArg::Type::BOOL, /* default */ "false",
+                 "Allow high fees"},
             },
             RPCResult{
                 "[                   (array) The result of the mempool "
                 "acceptance test for each raw transaction in the input array.\n"
                 "                            Length is exactly one for now.\n"
                 " {\n"
                 "  \"txid\"           (string) The transaction hash in hex\n"
                 "  \"allowed\"        (boolean) If the mempool allows this tx "
                 "to be inserted\n"
                 "  \"reject-reason\"  (string) Rejection string (only present "
                 "when 'allowed' is false)\n"
                 " }\n"
                 "]\n"},
             RPCExamples{
                 "\nCreate a transaction\n" +
                 HelpExampleCli(
                     "createrawtransaction",
                     "\"[{\\\"txid\\\" : \\\"mytxid\\\",\\\"vout\\\":0}]\" "
                     "\"{\\\"myaddress\\\":0.01}\"") +
                 "Sign the transaction, and get back the hex\n" +
                 HelpExampleCli("signrawtransactionwithwallet", "\"myhex\"") +
                 "\nTest acceptance of the transaction (signed hex)\n" +
                 HelpExampleCli("testmempoolaccept", "[\"signedhex\"]") +
                 "\nAs a JSON-RPC call\n" +
                 HelpExampleRpc("testmempoolaccept", "[\"signedhex\"]")},
         }
                                      .ToString());
     }
 
     RPCTypeCheck(request.params, {UniValue::VARR, UniValue::VBOOL});
     if (request.params[0].get_array().size() != 1) {
         throw JSONRPCError(
             RPC_INVALID_PARAMETER,
             "Array must contain exactly one raw transaction for now");
     }
 
     CMutableTransaction mtx;
     if (!DecodeHexTx(mtx, request.params[0].get_array()[0].get_str())) {
         throw JSONRPCError(RPC_DESERIALIZATION_ERROR, "TX decode failed");
     }
     CTransactionRef tx(MakeTransactionRef(std::move(mtx)));
     const uint256 &txid = tx->GetId();
 
     Amount max_raw_tx_fee = maxTxFee;
     if (!request.params[1].isNull() && request.params[1].get_bool()) {
         max_raw_tx_fee = Amount::zero();
     }
 
     UniValue result(UniValue::VARR);
     UniValue result_0(UniValue::VOBJ);
     result_0.pushKV("txid", txid.GetHex());
 
     CValidationState state;
     bool missing_inputs;
     bool test_accept_res;
     {
         LOCK(cs_main);
         test_accept_res = AcceptToMemoryPool(
             config, g_mempool, state, std::move(tx), &missing_inputs,
             false /* bypass_limits */, max_raw_tx_fee, true /* test_accept */);
     }
     result_0.pushKV("allowed", test_accept_res);
     if (!test_accept_res) {
         if (state.IsInvalid()) {
             result_0.pushKV("reject-reason",
                             strprintf("%i: %s", state.GetRejectCode(),
                                       state.GetRejectReason()));
         } else if (missing_inputs) {
             result_0.pushKV("reject-reason", "missing-inputs");
         } else {
             result_0.pushKV("reject-reason", state.GetRejectReason());
         }
     }
 
     result.push_back(std::move(result_0));
     return result;
 }
 
 static std::string WriteHDKeypath(std::vector<uint32_t> &keypath) {
     std::string keypath_str = "m";
     for (uint32_t num : keypath) {
         keypath_str += "/";
         bool hardened = false;
         if (num & 0x80000000) {
             hardened = true;
             num &= ~0x80000000;
         }
 
         keypath_str += std::to_string(num);
         if (hardened) {
             keypath_str += "'";
         }
     }
     return keypath_str;
 }
 
 static UniValue decodepsbt(const Config &config,
                            const JSONRPCRequest &request) {
     if (request.fHelp || request.params.size() != 1) {
         throw std::runtime_error(RPCHelpMan{
             "decodepsbt",
             "\nReturn a JSON object representing the serialized, "
             "base64-encoded partially signed Bitcoin transaction.\n",
             {
-                {"psbt", RPCArg::Type::STR, /* opt */ false,
-                 /* default_val */ "", "The PSBT base64 string"},
+                {"psbt", RPCArg::Type::STR, RPCArg::Optional::NO,
+                 "The PSBT base64 string"},
             },
             RPCResult{
                 "{\n"
                 "  \"tx\" : {                   (json object) The decoded "
                 "network-serialized unsigned transaction.\n"
                 "    ...                                      The layout is "
                 "the same as the output of decoderawtransaction.\n"
                 "  },\n"
                 "  \"unknown\" : {                (json object) The unknown "
                 "global fields\n"
                 "    \"key\" : \"value\"            (key-value pair) An "
                 "unknown key-value pair\n"
                 "     ...\n"
                 "  },\n"
                 "  \"inputs\" : [                 (array of json objects)\n"
                 "    {\n"
                 "      \"utxo\" : {            (json object, optional) "
                 "Transaction output for UTXOs\n"
                 "        \"amount\" : x.xxx,           (numeric) The value "
                 "in " +
                 CURRENCY_UNIT +
                 "\n"
                 "        \"scriptPubKey\" : {          (json object)\n"
                 "          \"asm\" : \"asm\",            (string) The asm\n"
                 "          \"hex\" : \"hex\",            (string) The hex\n"
                 "          \"type\" : \"pubkeyhash\",    (string) The type, eg "
                 "'pubkeyhash'\n"
                 "          \"address\" : \"address\"     (string) Bitcoin "
                 "address if there is one\n"
                 "        }\n"
                 "      },\n"
                 "      \"partial_signatures\" : {             (json object, "
                 "optional)\n"
                 "        \"pubkey\" : \"signature\",           (string) The "
                 "public key and signature that corresponds to it.\n"
                 "        ,...\n"
                 "      }\n"
                 "      \"sighash\" : \"type\",                  (string, "
                 "optional) The sighash type to be used\n"
                 "      \"redeem_script\" : {       (json object, optional)\n"
                 "          \"asm\" : \"asm\",            (string) The asm\n"
                 "          \"hex\" : \"hex\",            (string) The hex\n"
                 "          \"type\" : \"pubkeyhash\",    (string) The type, eg "
                 "'pubkeyhash'\n"
                 "        }\n"
                 "      \"bip32_derivs\" : {          (json object, optional)\n"
                 "        \"pubkey\" : {                     (json object, "
                 "optional) The public key with the derivation path as the "
                 "value.\n"
                 "          \"master_fingerprint\" : \"fingerprint\"     "
                 "(string) The fingerprint of the master key\n"
                 "          \"path\" : \"path\",                         "
                 "(string) The path\n"
                 "        }\n"
                 "        ,...\n"
                 "      }\n"
                 "      \"final_scriptsig\" : {       (json object, optional)\n"
                 "          \"asm\" : \"asm\",            (string) The asm\n"
                 "          \"hex\" : \"hex\",            (string) The hex\n"
                 "        }\n"
                 "      \"unknown\" : {                (json object) The "
                 "unknown global fields\n"
                 "        \"key\" : \"value\"            (key-value pair) An "
                 "unknown key-value pair\n"
                 "         ...\n"
                 "      },\n"
                 "    }\n"
                 "    ,...\n"
                 "  ]\n"
                 "  \"outputs\" : [                 (array of json objects)\n"
                 "    {\n"
                 "      \"redeem_script\" : {       (json object, optional)\n"
                 "          \"asm\" : \"asm\",            (string) The asm\n"
                 "          \"hex\" : \"hex\",            (string) The hex\n"
                 "          \"type\" : \"pubkeyhash\",    (string) The type, eg "
                 "'pubkeyhash'\n"
                 "        }\n"
                 "      \"bip32_derivs\" : [          (array of json objects, "
                 "optional)\n"
                 "        {\n"
                 "          \"pubkey\" : \"pubkey\",                     "
                 "(string) The public key this path corresponds to\n"
                 "          \"master_fingerprint\" : \"fingerprint\"     "
                 "(string) The fingerprint of the master key\n"
                 "          \"path\" : \"path\",                         "
                 "(string) The path\n"
                 "          }\n"
                 "        }\n"
                 "        ,...\n"
                 "      ],\n"
                 "      \"unknown\" : {                (json object) The "
                 "unknown global fields\n"
                 "        \"key\" : \"value\"            (key-value pair) An "
                 "unknown key-value pair\n"
                 "         ...\n"
                 "      },\n"
                 "    }\n"
                 "    ,...\n"
                 "  ]\n"
                 "  \"fee\" : fee                      (numeric, optional) The "
                 "transaction fee paid if all UTXOs slots in the PSBT have been "
                 "filled.\n"
                 "}\n"},
             RPCExamples{HelpExampleCli("decodepsbt", "\"psbt\"")},
         }
                                      .ToString());
     }
 
     RPCTypeCheck(request.params, {UniValue::VSTR});
 
     // Unserialize the transactions
     PartiallySignedTransaction psbtx;
     std::string error;
     if (!DecodeBase64PSBT(psbtx, request.params[0].get_str(), error)) {
         throw JSONRPCError(RPC_DESERIALIZATION_ERROR,
                            strprintf("TX decode failed %s", error));
     }
 
     UniValue result(UniValue::VOBJ);
 
     // Add the decoded tx
     UniValue tx_univ(UniValue::VOBJ);
     TxToUniv(CTransaction(*psbtx.tx), uint256(), tx_univ, false);
     result.pushKV("tx", tx_univ);
 
     // Unknown data
     if (psbtx.unknown.size() > 0) {
         UniValue unknowns(UniValue::VOBJ);
         for (auto entry : psbtx.unknown) {
             unknowns.pushKV(HexStr(entry.first), HexStr(entry.second));
         }
         result.pushKV("unknown", unknowns);
     }
 
     // inputs
     Amount total_in = Amount::zero();
     bool have_all_utxos = true;
     UniValue inputs(UniValue::VARR);
     for (size_t i = 0; i < psbtx.inputs.size(); ++i) {
         const PSBTInput &input = psbtx.inputs[i];
         UniValue in(UniValue::VOBJ);
         // UTXOs
         if (!input.utxo.IsNull()) {
             const CTxOut &txout = input.utxo;
 
             UniValue out(UniValue::VOBJ);
 
             out.pushKV("amount", ValueFromAmount(txout.nValue));
             total_in += txout.nValue;
 
             UniValue o(UniValue::VOBJ);
             ScriptToUniv(txout.scriptPubKey, o, true);
             out.pushKV("scriptPubKey", o);
             in.pushKV("utxo", out);
         } else {
             have_all_utxos = false;
         }
 
         // Partial sigs
         if (!input.partial_sigs.empty()) {
             UniValue partial_sigs(UniValue::VOBJ);
             for (const auto &sig : input.partial_sigs) {
                 partial_sigs.pushKV(HexStr(sig.second.first),
                                     HexStr(sig.second.second));
             }
             in.pushKV("partial_signatures", partial_sigs);
         }
 
         // Sighash
         uint8_t sighashbyte = input.sighash_type.getRawSigHashType() & 0xff;
         if (sighashbyte > 0) {
             in.pushKV("sighash", SighashToStr(sighashbyte));
         }
 
         // Redeem script
         if (!input.redeem_script.empty()) {
             UniValue r(UniValue::VOBJ);
             ScriptToUniv(input.redeem_script, r, false);
             in.pushKV("redeem_script", r);
         }
 
         // keypaths
         if (!input.hd_keypaths.empty()) {
             UniValue keypaths(UniValue::VARR);
             for (auto entry : input.hd_keypaths) {
                 UniValue keypath(UniValue::VOBJ);
                 keypath.pushKV("pubkey", HexStr(entry.first));
 
                 keypath.pushKV(
                     "master_fingerprint",
                     strprintf("%08x", ReadBE32(entry.second.fingerprint)));
                 keypath.pushKV("path", WriteHDKeypath(entry.second.path));
                 keypaths.push_back(keypath);
             }
             in.pushKV("bip32_derivs", keypaths);
         }
 
         // Final scriptSig
         if (!input.final_script_sig.empty()) {
             UniValue scriptsig(UniValue::VOBJ);
             scriptsig.pushKV("asm",
                              ScriptToAsmStr(input.final_script_sig, true));
             scriptsig.pushKV("hex", HexStr(input.final_script_sig));
             in.pushKV("final_scriptSig", scriptsig);
         }
 
         // Unknown data
         if (input.unknown.size() > 0) {
             UniValue unknowns(UniValue::VOBJ);
             for (auto entry : input.unknown) {
                 unknowns.pushKV(HexStr(entry.first), HexStr(entry.second));
             }
             in.pushKV("unknown", unknowns);
         }
 
         inputs.push_back(in);
     }
     result.pushKV("inputs", inputs);
 
     // outputs
     Amount output_value = Amount::zero();
     UniValue outputs(UniValue::VARR);
     for (size_t i = 0; i < psbtx.outputs.size(); ++i) {
         const PSBTOutput &output = psbtx.outputs[i];
         UniValue out(UniValue::VOBJ);
         // Redeem script
         if (!output.redeem_script.empty()) {
             UniValue r(UniValue::VOBJ);
             ScriptToUniv(output.redeem_script, r, false);
             out.pushKV("redeem_script", r);
         }
 
         // keypaths
         if (!output.hd_keypaths.empty()) {
             UniValue keypaths(UniValue::VARR);
             for (auto entry : output.hd_keypaths) {
                 UniValue keypath(UniValue::VOBJ);
                 keypath.pushKV("pubkey", HexStr(entry.first));
                 keypath.pushKV(
                     "master_fingerprint",
                     strprintf("%08x", ReadBE32(entry.second.fingerprint)));
                 keypath.pushKV("path", WriteHDKeypath(entry.second.path));
                 keypaths.push_back(keypath);
             }
             out.pushKV("bip32_derivs", keypaths);
         }
 
         // Unknown data
         if (output.unknown.size() > 0) {
             UniValue unknowns(UniValue::VOBJ);
             for (auto entry : output.unknown) {
                 unknowns.pushKV(HexStr(entry.first), HexStr(entry.second));
             }
             out.pushKV("unknown", unknowns);
         }
 
         outputs.push_back(out);
 
         // Fee calculation
         output_value += psbtx.tx->vout[i].nValue;
     }
     result.pushKV("outputs", outputs);
     if (have_all_utxos) {
         result.pushKV("fee", ValueFromAmount(total_in - output_value));
     }
 
     return result;
 }
 
 static UniValue combinepsbt(const Config &config,
                             const JSONRPCRequest &request) {
     if (request.fHelp || request.params.size() != 1) {
         throw std::runtime_error(RPCHelpMan{
             "combinepsbt",
             "\nCombine multiple partially signed Bitcoin transactions into "
             "one transaction.\n"
             "Implements the Combiner role.\n",
             {
                 {
                     "txs",
                     RPCArg::Type::ARR,
-                    /* opt */ false,
-                    /* default_val */ "",
+                    RPCArg::Optional::NO,
                     "A json array of base64 strings of partially signed "
                     "transactions",
                     {
-                        {"psbt", RPCArg::Type::STR, /* opt */ false,
-                         /* default_val */ "", "A base64 string of a PSBT"},
+                        {"psbt", RPCArg::Type::STR, RPCArg::Optional::OMITTED,
+                         "A base64 string of a PSBT"},
                     },
                 },
             },
             RPCResult{"  \"psbt\"          (string) The base64-encoded "
                       "partially signed transaction\n"},
             RPCExamples{HelpExampleCli(
                 "combinepsbt",
                 "[\"mybase64_1\", \"mybase64_2\", \"mybase64_3\"]")},
         }
                                      .ToString());
     }
 
     RPCTypeCheck(request.params, {UniValue::VARR}, true);
 
     // Unserialize the transactions
     std::vector<PartiallySignedTransaction> psbtxs;
     UniValue txs = request.params[0].get_array();
     for (size_t i = 0; i < txs.size(); ++i) {
         PartiallySignedTransaction psbtx;
         std::string error;
         if (!DecodeBase64PSBT(psbtx, txs[i].get_str(), error)) {
             throw JSONRPCError(RPC_DESERIALIZATION_ERROR,
                                strprintf("TX decode failed %s", error));
         }
         psbtxs.push_back(psbtx);
     }
 
     PartiallySignedTransaction merged_psbt;
     const TransactionError error = CombinePSBTs(merged_psbt, psbtxs);
     if (error != TransactionError::OK) {
         throw JSONRPCTransactionError(error);
     }
 
     UniValue result(UniValue::VOBJ);
     CDataStream ssTx(SER_NETWORK, PROTOCOL_VERSION);
     ssTx << merged_psbt;
     return EncodeBase64((uint8_t *)ssTx.data(), ssTx.size());
 }
 
 static UniValue finalizepsbt(const Config &config,
                              const JSONRPCRequest &request) {
     if (request.fHelp || request.params.size() < 1 ||
         request.params.size() > 2) {
         throw std::runtime_error(RPCHelpMan{
             "finalizepsbt",
             "Finalize the inputs of a PSBT. If the transaction is "
             "fully signed, it will produce a\n"
             "network serialized transaction which can be broadcast "
             "with sendrawtransaction. Otherwise a PSBT will be\n"
             "created which has the final_scriptSigfields filled for "
             "inputs that are complete.\n"
             "Implements the Finalizer and Extractor roles.\n",
             {
-                {"psbt", RPCArg::Type::STR, /* opt */ false,
-                 /* default_val */ "", "A base64 string of a PSBT"},
-                {"extract", RPCArg::Type::BOOL, /* opt */ true,
-                 /* default_val */ "true",
+                {"psbt", RPCArg::Type::STR, RPCArg::Optional::NO,
+                 "A base64 string of a PSBT"},
+                {"extract", RPCArg::Type::BOOL, /* default */ "true",
                  "If true and the transaction is complete,\n"
                  "                             extract and return the complete "
                  "transaction in normal network serialization instead of the "
                  "PSBT."},
             },
             RPCResult{
                 "{\n"
                 "  \"psbt\" : \"value\",          (string) The base64-encoded "
                 "partially signed transaction if not extracted\n"
                 "  \"hex\" : \"value\",           (string) The hex-encoded "
                 "network transaction if extracted\n"
                 "  \"complete\" : true|false,   (boolean) If the transaction "
                 "has a complete set of signatures\n"
                 "  ]\n"
                 "}\n"},
             RPCExamples{HelpExampleCli("finalizepsbt", "\"psbt\"")},
         }
                                      .ToString());
     }
 
     RPCTypeCheck(request.params, {UniValue::VSTR, UniValue::VBOOL}, true);
 
     // Unserialize the transactions
     PartiallySignedTransaction psbtx;
     std::string error;
     if (!DecodeBase64PSBT(psbtx, request.params[0].get_str(), error)) {
         throw JSONRPCError(RPC_DESERIALIZATION_ERROR,
                            strprintf("TX decode failed %s", error));
     }
 
     bool extract = request.params[1].isNull() || (!request.params[1].isNull() &&
                                                   request.params[1].get_bool());
 
     CMutableTransaction mtx;
     bool complete = FinalizeAndExtractPSBT(psbtx, mtx);
 
     UniValue result(UniValue::VOBJ);
     CDataStream ssTx(SER_NETWORK, PROTOCOL_VERSION);
     std::string result_str;
 
     if (complete && extract) {
         ssTx << mtx;
         result_str = HexStr(ssTx.str());
         result.pushKV("hex", result_str);
     } else {
         ssTx << psbtx;
         result_str = EncodeBase64(ssTx.str());
         result.pushKV("psbt", result_str);
     }
     result.pushKV("complete", complete);
 
     return result;
 }
 
 static UniValue createpsbt(const Config &config,
                            const JSONRPCRequest &request) {
     if (request.fHelp || request.params.size() < 2 ||
         request.params.size() > 3) {
         throw std::runtime_error(RPCHelpMan{
             "createpsbt",
             "\nCreates a transaction in the Partially Signed Transaction "
             "format.\n"
             "Implements the Creator role.\n",
             {
                 {
                     "inputs",
                     RPCArg::Type::ARR,
-                    /* opt */ false,
-                    /* default_val */ "",
+                    RPCArg::Optional::NO,
                     "A json array of json objects",
                     {
                         {
                             "",
                             RPCArg::Type::OBJ,
-                            /* opt */ false,
-                            /* default_val */ "",
+                            RPCArg::Optional::OMITTED,
                             "",
                             {
                                 {"txid", RPCArg::Type::STR_HEX,
-                                 /* opt */ false, /* default_val */ "",
-                                 "The transaction id"},
-                                {"vout", RPCArg::Type::NUM, /* opt */ false,
-                                 /* default_val */ "", "The output number"},
-                                {"sequence", RPCArg::Type::NUM, /* opt */ true,
-                                 /* default_val */
+                                 RPCArg::Optional::NO, "The transaction id"},
+                                {"vout", RPCArg::Type::NUM,
+                                 RPCArg::Optional::NO, "The output number"},
+                                {"sequence", RPCArg::Type::NUM, /* default */
                                  "depends on the value of the 'locktime' "
                                  "argument",
                                  "The sequence number"},
                             },
                         },
                     },
                 },
                 {
                     "outputs",
                     RPCArg::Type::ARR,
-                    /* opt */ false,
-                    /* default_val */ "",
+                    RPCArg::Optional::NO,
                     "a json array with outputs (key-value pairs).\n"
                     "For compatibility reasons, a dictionary, which holds "
                     "the key-value pairs directly, is also\n"
                     "                             accepted as second "
                     "parameter.",
                     {
                         {
                             "",
                             RPCArg::Type::OBJ,
-                            /* opt */ true,
-                            /* default_val */ "",
+                            RPCArg::Optional::OMITTED,
                             "",
                             {
                                 {"address", RPCArg::Type::AMOUNT,
-                                 /* opt */ false, /* default_val */ "",
+                                 RPCArg::Optional::NO,
                                  "A key-value pair. The key (string) is "
                                  "the bitcoin address, the value (float or "
                                  "string) is the amount in " +
                                      CURRENCY_UNIT},
                             },
                         },
                         {
                             "",
                             RPCArg::Type::OBJ,
-                            /* opt */ true,
-                            /* default_val */ "",
+                            RPCArg::Optional::OMITTED,
                             "",
                             {
                                 {"data", RPCArg::Type::STR_HEX,
-                                 /* opt */ false, /* default_val */ "",
+                                 RPCArg::Optional::NO,
                                  "A key-value pair. The key must be "
                                  "\"data\", the value is hex-encoded data"},
                             },
                         },
                     },
                 },
-                {"locktime", RPCArg::Type::NUM, /* opt */ true,
-                 /* default_val */ "0",
+                {"locktime", RPCArg::Type::NUM, /* default */ "0",
                  "Raw locktime. Non-0 value also locktime-activates inputs"},
             },
             RPCResult{"  \"psbt\"        (string)  The resulting raw "
                       "transaction (base64-encoded string)\n"},
             RPCExamples{HelpExampleCli(
                 "createpsbt", "\"[{\\\"txid\\\":\\\"myid\\\",\\\"vout\\\":0}]"
                               "\" \"[{\\\"data\\\":\\\"00010203\\\"}]\"")},
         }
                                      .ToString());
     }
 
     RPCTypeCheck(request.params,
                  {
                      UniValue::VARR,
                      UniValueType(), // ARR or OBJ, checked later
                      UniValue::VNUM,
                  },
                  true);
 
     CMutableTransaction rawTx =
         ConstructTransaction(config.GetChainParams(), request.params[0],
                              request.params[1], request.params[2]);
 
     // Make a blank psbt
     PartiallySignedTransaction psbtx;
     psbtx.tx = rawTx;
     for (size_t i = 0; i < rawTx.vin.size(); ++i) {
         psbtx.inputs.push_back(PSBTInput());
     }
     for (size_t i = 0; i < rawTx.vout.size(); ++i) {
         psbtx.outputs.push_back(PSBTOutput());
     }
 
     // Serialize the PSBT
     CDataStream ssTx(SER_NETWORK, PROTOCOL_VERSION);
     ssTx << psbtx;
 
     return EncodeBase64((uint8_t *)ssTx.data(), ssTx.size());
 }
 
 static UniValue converttopsbt(const Config &config,
                               const JSONRPCRequest &request) {
     if (request.fHelp || request.params.size() < 1 ||
         request.params.size() > 2) {
         throw std::runtime_error(RPCHelpMan{
             "converttopsbt",
             "\nConverts a network serialized transaction to a PSBT. "
             "This should be used only with createrawtransaction and "
             "fundrawtransaction\n"
             "createpsbt and walletcreatefundedpsbt should be used for new "
             "applications.\n",
             {
-                {"hexstring", RPCArg::Type::STR_HEX, /* opt */ false,
-                 /* default_val */ "", "The hex string of a raw transaction"},
-                {"permitsigdata", RPCArg::Type::BOOL, /* opt */ true,
-                 /* default_val */ "false",
+                {"hexstring", RPCArg::Type::STR_HEX, RPCArg::Optional::NO,
+                 "The hex string of a raw transaction"},
+                {"permitsigdata", RPCArg::Type::BOOL, /* default */ "false",
                  "If true, any signatures in the input will be discarded and "
                  "conversion.\n"
                  "                              will continue. If false, RPC "
                  "will fail if any signatures are present."},
             },
             RPCResult{"  \"psbt\"        (string)  The resulting raw "
                       "transaction (base64-encoded string)\n"},
             RPCExamples{
                 "\nCreate a transaction\n" +
                 HelpExampleCli("createrawtransaction",
                                "\"[{\\\"txid\\\":\\\"myid\\\",\\\"vout\\\":0}]"
                                "\" \"[{\\\"data\\\":\\\"00010203\\\"}]\"") +
                 "\nConvert the transaction to a PSBT\n" +
                 HelpExampleCli("converttopsbt", "\"rawtransaction\"")},
         }
                                      .ToString());
     }
 
     RPCTypeCheck(request.params, {UniValue::VSTR, UniValue::VBOOL}, true);
 
     // parse hex string from parameter
     CMutableTransaction tx;
     bool permitsigdata =
         request.params[1].isNull() ? false : request.params[1].get_bool();
     if (!DecodeHexTx(tx, request.params[0].get_str())) {
         throw JSONRPCError(RPC_DESERIALIZATION_ERROR, "TX decode failed");
     }
 
     // Remove all scriptSigs from inputs
     for (CTxIn &input : tx.vin) {
         if (!input.scriptSig.empty() && !permitsigdata) {
             throw JSONRPCError(RPC_DESERIALIZATION_ERROR,
                                "Inputs must not have scriptSigs");
         }
         input.scriptSig.clear();
     }
 
     // Make a blank psbt
     PartiallySignedTransaction psbtx;
     psbtx.tx = tx;
     for (size_t i = 0; i < tx.vin.size(); ++i) {
         psbtx.inputs.push_back(PSBTInput());
     }
     for (size_t i = 0; i < tx.vout.size(); ++i) {
         psbtx.outputs.push_back(PSBTOutput());
     }
 
     // Serialize the PSBT
     CDataStream ssTx(SER_NETWORK, PROTOCOL_VERSION);
     ssTx << psbtx;
 
     return EncodeBase64((uint8_t *)ssTx.data(), ssTx.size());
 }
 
 UniValue utxoupdatepsbt(const Config &config, const JSONRPCRequest &request) {
     if (request.fHelp || request.params.size() != 1) {
         throw std::runtime_error(RPCHelpMan{
             "utxoupdatepsbt",
             "\nUpdates a PSBT with witness UTXOs retrieved from the UTXO set "
             "or the mempool.\n",
-            {{"psbt", RPCArg::Type::STR,
-              /* opt */ false, /* default_val */ "",
+            {{"psbt", RPCArg::Type::STR, RPCArg::Optional::NO,
               "A base64 string of a PSBT"}},
             RPCResult{"  \"psbt\"          (string) The base64-encoded "
                       "partially signed transaction with inputs updated\n"},
             RPCExamples{HelpExampleCli("utxoupdatepsbt", "\"psbt\"")}}
                                      .ToString());
     }
 
     RPCTypeCheck(request.params, {UniValue::VSTR}, true);
 
     // Unserialize the transactions
     PartiallySignedTransaction psbtx;
     std::string error;
     if (!DecodeBase64PSBT(psbtx, request.params[0].get_str(), error)) {
         throw JSONRPCError(RPC_DESERIALIZATION_ERROR,
                            strprintf("TX decode failed %s", error));
     }
 
     // Fetch previous transactions (inputs):
     CCoinsView viewDummy;
     CCoinsViewCache view(&viewDummy);
     {
         LOCK2(cs_main, g_mempool.cs);
         CCoinsViewCache &viewChain = *pcoinsTip;
         CCoinsViewMemPool viewMempool(&viewChain, g_mempool);
         // temporarily switch cache backend to db+mempool view
         view.SetBackend(viewMempool);
 
         for (const CTxIn &txin : psbtx.tx->vin) {
             // Load entries from viewChain into view; can fail.
             view.AccessCoin(txin.prevout);
         }
 
         // switch back to avoid locking mempool for too long
         view.SetBackend(viewDummy);
     }
 
     // Fill the inputs
     for (size_t i = 0; i < psbtx.tx->vin.size(); ++i) {
         PSBTInput &input = psbtx.inputs.at(i);
 
         if (!input.utxo.IsNull()) {
             continue;
         }
 
         input.utxo = view.AccessCoin(psbtx.tx->vin[i].prevout).GetTxOut();
     }
 
     CDataStream ssTx(SER_NETWORK, PROTOCOL_VERSION);
     ssTx << psbtx;
     return EncodeBase64((uint8_t *)ssTx.data(), ssTx.size());
 }
 
 UniValue joinpsbts(const Config &config, const JSONRPCRequest &request) {
     if (request.fHelp || request.params.size() != 1) {
         throw std::runtime_error(RPCHelpMan{
             "joinpsbts",
             "\nJoins multiple distinct PSBTs with different inputs and outputs "
             "into one PSBT with inputs and outputs from all of the PSBTs\n"
             "No input in any of the PSBTs can be in more than one of the "
             "PSBTs.\n",
             {{"txs",
               RPCArg::Type::ARR,
-              /* opt */ false,
-              /* default_val */ "",
+              RPCArg::Optional::NO,
               "A json array of base64 strings of partially signed transactions",
-              {{"psbt", RPCArg::Type::STR, /* opt */ false,
-                /* default_val */ "", "A base64 string of a PSBT"}}}},
+              {{"psbt", RPCArg::Type::STR, RPCArg::Optional::NO,
+                "A base64 string of a PSBT"}}}},
             RPCResult{"  \"psbt\"          (string) The base64-encoded "
                       "partially signed transaction\n"},
             RPCExamples{HelpExampleCli("joinpsbts", "\"psbt\"")}}
                                      .ToString());
     }
 
     RPCTypeCheck(request.params, {UniValue::VARR}, true);
 
     // Unserialize the transactions
     std::vector<PartiallySignedTransaction> psbtxs;
     UniValue txs = request.params[0].get_array();
 
     if (txs.size() <= 1) {
         throw JSONRPCError(RPC_INVALID_PARAMETER,
                            "At least two PSBTs are required to join PSBTs.");
     }
 
     int32_t best_version = 1;
     uint32_t best_locktime = 0xffffffff;
     for (size_t i = 0; i < txs.size(); ++i) {
         PartiallySignedTransaction psbtx;
         std::string error;
         if (!DecodeBase64PSBT(psbtx, txs[i].get_str(), error)) {
             throw JSONRPCError(RPC_DESERIALIZATION_ERROR,
                                strprintf("TX decode failed %s", error));
         }
         psbtxs.push_back(psbtx);
         // Choose the highest version number
         if (psbtx.tx->nVersion > best_version) {
             best_version = psbtx.tx->nVersion;
         }
         // Choose the lowest lock time
         if (psbtx.tx->nLockTime < best_locktime) {
             best_locktime = psbtx.tx->nLockTime;
         }
     }
 
     // Create a blank psbt where everything will be added
     PartiallySignedTransaction merged_psbt;
     merged_psbt.tx = CMutableTransaction();
     merged_psbt.tx->nVersion = best_version;
     merged_psbt.tx->nLockTime = best_locktime;
 
     // Merge
     for (auto &psbt : psbtxs) {
         for (size_t i = 0; i < psbt.tx->vin.size(); ++i) {
             if (!merged_psbt.AddInput(psbt.tx->vin[i], psbt.inputs[i])) {
                 throw JSONRPCError(
                     RPC_INVALID_PARAMETER,
                     strprintf(
                         "Input %s:%d exists in multiple PSBTs",
                         psbt.tx->vin[i].prevout.GetTxId().ToString().c_str(),
                         psbt.tx->vin[i].prevout.GetN()));
             }
         }
         for (size_t i = 0; i < psbt.tx->vout.size(); ++i) {
             merged_psbt.AddOutput(psbt.tx->vout[i], psbt.outputs[i]);
         }
         merged_psbt.unknown.insert(psbt.unknown.begin(), psbt.unknown.end());
     }
 
     CDataStream ssTx(SER_NETWORK, PROTOCOL_VERSION);
     ssTx << merged_psbt;
     return EncodeBase64((uint8_t *)ssTx.data(), ssTx.size());
 }
 
 UniValue analyzepsbt(const Config &config, const JSONRPCRequest &request) {
     if (request.fHelp || request.params.size() != 1) {
         throw std::runtime_error(RPCHelpMan{
             "analyzepsbt",
             "\nAnalyzes and provides information about the current status of a "
             "PSBT and its inputs\n",
-            {{"psbt", RPCArg::Type::STR, /* opt */ false, /* default_var */ "",
+            {{"psbt", RPCArg::Type::STR, RPCArg::Optional::NO,
               "A base64 string of a PSBT"}},
             RPCResult{
                 "{\n"
                 "  \"inputs\" : [                      (array of json "
                 "objects)\n"
                 "    {\n"
                 "      \"has_utxo\" : true|false     (boolean) Whether a UTXO "
                 "is provided\n"
                 "      \"is_final\" : true|false     (boolean) Whether the "
                 "input is finalized\n"
                 "      \"missing\" : {               (json object, optional) "
                 "Things that are missing that are required to complete this "
                 "input\n"
                 "        \"pubkeys\" : [             (array)\n"
                 "          \"keyid\"                 (string) Public key ID, "
                 "hash160 of the public key, of a public key whose BIP 32 "
                 "derivation path is missing\n"
                 "        ]\n"
                 "        \"signatures\" : [          (array)\n"
                 "          \"keyid\"                 (string) Public key ID, "
                 "hash160 of the public key, of a public key whose signature is "
                 "missing\n"
                 "        ]\n"
                 "        \"redeemscript\" : \"hash\"   (string) Hash160 of the "
                 "redeemScript that is missing\n"
                 "      }\n"
                 "      \"next\" : \"role\"           (string) Role of the next "
                 "person that this input needs to go to\n"
                 "    }\n"
                 "    ,...\n"
                 "  ]\n"
                 "  \"estimated_vsize\" : vsize       (numeric) Estimated vsize "
                 "of the final signed transaction\n"
                 "  \"estimated_feerate\" : feerate   (numeric, optional) "
                 "Estimated feerate of the final signed transaction. Shown only "
                 "if all UTXO slots in the PSBT have been filled.\n"
                 "  \"fee\" : fee                     (numeric, optional) The "
                 "transaction fee paid. Shown only if all UTXO slots in the "
                 "PSBT have been filled.\n"
                 "  \"next\" : \"role\"                 (string) Role of the "
                 "next person that this psbt needs to go to\n"
                 "}\n"},
             RPCExamples{HelpExampleCli("analyzepsbt", "\"psbt\"")}}
                                      .ToString());
     }
 
     RPCTypeCheck(request.params, {UniValue::VSTR});
 
     // Unserialize the transaction
     PartiallySignedTransaction psbtx;
     std::string error;
     if (!DecodeBase64PSBT(psbtx, request.params[0].get_str(), error)) {
         throw JSONRPCError(RPC_DESERIALIZATION_ERROR,
                            strprintf("TX decode failed %s", error));
     }
 
     PSBTAnalysis psbta = AnalyzePSBT(psbtx);
 
     UniValue result(UniValue::VOBJ);
     UniValue inputs_result(UniValue::VARR);
     for (const auto &input : psbta.inputs) {
         UniValue input_univ(UniValue::VOBJ);
         UniValue missing(UniValue::VOBJ);
 
         input_univ.pushKV("has_utxo", input.has_utxo);
         input_univ.pushKV("is_final", input.is_final);
         input_univ.pushKV("next", PSBTRoleName(input.next));
 
         if (!input.missing_pubkeys.empty()) {
             UniValue missing_pubkeys_univ(UniValue::VARR);
             for (const CKeyID &pubkey : input.missing_pubkeys) {
                 missing_pubkeys_univ.push_back(HexStr(pubkey));
             }
             missing.pushKV("pubkeys", missing_pubkeys_univ);
         }
         if (!input.missing_redeem_script.IsNull()) {
             missing.pushKV("redeemscript", HexStr(input.missing_redeem_script));
         }
         if (!input.missing_sigs.empty()) {
             UniValue missing_sigs_univ(UniValue::VARR);
             for (const CKeyID &pubkey : input.missing_sigs) {
                 missing_sigs_univ.push_back(HexStr(pubkey));
             }
             missing.pushKV("signatures", missing_sigs_univ);
         }
         if (!missing.getKeys().empty()) {
             input_univ.pushKV("missing", missing);
         }
         inputs_result.push_back(input_univ);
     }
     result.pushKV("inputs", inputs_result);
 
     if (psbta.estimated_vsize != nullopt) {
         result.pushKV("estimated_vsize", (int)*psbta.estimated_vsize);
     }
     if (psbta.estimated_feerate != nullopt) {
         result.pushKV("estimated_feerate",
                       ValueFromAmount(psbta.estimated_feerate->GetFeePerK()));
     }
     if (psbta.fee != nullopt) {
         result.pushKV("fee", ValueFromAmount(*psbta.fee));
     }
     result.pushKV("next", PSBTRoleName(psbta.next));
 
     return result;
 }
 
 // clang-format off
 static const CRPCCommand commands[] = {
     //  category            name                         actor (function)           argNames
     //  ------------------- ------------------------     ----------------------     ----------
     { "rawtransactions",    "getrawtransaction",         getrawtransaction,         {"txid","verbose","blockhash"} },
     { "rawtransactions",    "createrawtransaction",      createrawtransaction,      {"inputs","outputs","locktime"} },
     { "rawtransactions",    "decoderawtransaction",      decoderawtransaction,      {"hexstring"} },
     { "rawtransactions",    "decodescript",              decodescript,              {"hexstring"} },
     { "rawtransactions",    "sendrawtransaction",        sendrawtransaction,        {"hexstring","allowhighfees"} },
     { "rawtransactions",    "combinerawtransaction",     combinerawtransaction,     {"txs"} },
     { "rawtransactions",    "signrawtransactionwithkey", signrawtransactionwithkey, {"hexstring","privkeys","prevtxs","sighashtype"} },
     { "rawtransactions",    "testmempoolaccept",         testmempoolaccept,         {"rawtxs","allowhighfees"} },
     { "rawtransactions",    "decodepsbt",                decodepsbt,                {"psbt"} },
     { "rawtransactions",    "combinepsbt",               combinepsbt,               {"txs"} },
     { "rawtransactions",    "finalizepsbt",              finalizepsbt,              {"psbt", "extract"} },
     { "rawtransactions",    "createpsbt",                createpsbt,                {"inputs","outputs","locktime"} },
     { "rawtransactions",    "converttopsbt",             converttopsbt,             {"hexstring","permitsigdata"} },
     { "rawtransactions",    "utxoupdatepsbt",            utxoupdatepsbt,            {"psbt"} },
     { "rawtransactions",    "joinpsbts",                 joinpsbts,                 {"txs"} },
     { "rawtransactions",    "analyzepsbt",               analyzepsbt,               {"psbt"} },
     { "blockchain",         "gettxoutproof",             gettxoutproof,             {"txids", "blockhash"} },
     { "blockchain",         "verifytxoutproof",          verifytxoutproof,          {"proof"} },
 };
 // clang-format on
 
 void RegisterRawTransactionRPCCommands(CRPCTable &t) {
     for (unsigned int vcidx = 0; vcidx < ARRAYLEN(commands); vcidx++) {
         t.appendCommand(commands[vcidx].name, &commands[vcidx]);
     }
 }
diff --git a/src/rpc/server.cpp b/src/rpc/server.cpp
index c16122d82..3e9e1324d 100644
--- a/src/rpc/server.cpp
+++ b/src/rpc/server.cpp
@@ -1,537 +1,536 @@
 // Copyright (c) 2010 Satoshi Nakamoto
 // Copyright (c) 2009-2018 The Bitcoin Core developers
 // Copyright (c) 2018-2019 The Bitcoin developers
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
 #include <rpc/server.h>
 
 #include <config.h>
 #include <fs.h>
 #include <key_io.h>
 #include <random.h>
 #include <rpc/util.h>
 #include <shutdown.h>
 #include <sync.h>
 #include <ui_interface.h>
 #include <util/strencodings.h>
 #include <util/system.h>
 
 #include <univalue.h>
 
 #include <boost/algorithm/string/classification.hpp>
 #include <boost/algorithm/string/split.hpp>
 #include <boost/signals2/signal.hpp>
 
 #include <memory> // for unique_ptr
 #include <set>
 #include <unordered_map>
 
 static std::atomic<bool> g_rpc_running{false};
 static bool fRPCInWarmup = true;
 static std::string rpcWarmupStatus("RPC server started");
 static RecursiveMutex cs_rpcWarmup;
 /* Timer-creating functions */
 static RPCTimerInterface *timerInterface = nullptr;
 /* Map of name to timer. */
 static std::map<std::string, std::unique_ptr<RPCTimerBase>> deadlineTimers;
 static bool ExecuteCommand(Config &config, const CRPCCommand &command,
                            const JSONRPCRequest &request, UniValue &result,
                            bool last_handler);
 
 struct RPCCommandExecutionInfo {
     std::string method;
     int64_t start;
 };
 
 struct RPCServerInfo {
     Mutex mutex;
     std::list<RPCCommandExecutionInfo> active_commands GUARDED_BY(mutex);
 };
 
 static RPCServerInfo g_rpc_server_info;
 
 struct RPCCommandExecution {
     std::list<RPCCommandExecutionInfo>::iterator it;
     explicit RPCCommandExecution(const std::string &method) {
         LOCK(g_rpc_server_info.mutex);
         it = g_rpc_server_info.active_commands.insert(
             g_rpc_server_info.active_commands.cend(),
             {method, GetTimeMicros()});
     }
     ~RPCCommandExecution() {
         LOCK(g_rpc_server_info.mutex);
         g_rpc_server_info.active_commands.erase(it);
     }
 };
 
 UniValue RPCServer::ExecuteCommand(Config &config,
                                    const JSONRPCRequest &request) const {
     // Return immediately if in warmup
     // This is retained from the old RPC implementation because a lot of state
     // is set during warmup that RPC commands may depend on.  This can be
     // safely removed once global variable usage has been eliminated.
     {
         LOCK(cs_rpcWarmup);
         if (fRPCInWarmup) {
             throw JSONRPCError(RPC_IN_WARMUP, rpcWarmupStatus);
         }
     }
 
     std::string commandName = request.strMethod;
     {
         auto commandsReadView = commands.getReadView();
         auto iter = commandsReadView->find(commandName);
         if (iter != commandsReadView.end()) {
             return iter->second.get()->Execute(request);
         }
     }
 
     // TODO Remove the below call to tableRPC.execute() and only call it for
     // context-free RPC commands via an implementation of RPCCommand.
 
     // Check if context-free RPC method is valid and execute it
     return tableRPC.execute(config, request);
 }
 
 void RPCServer::RegisterCommand(std::unique_ptr<RPCCommand> command) {
     if (command != nullptr) {
         const std::string &commandName = command->GetName();
         commands.getWriteView()->insert(
             std::make_pair(commandName, std::move(command)));
     }
 }
 
 static struct CRPCSignals {
     boost::signals2::signal<void()> Started;
     boost::signals2::signal<void()> Stopped;
 } g_rpcSignals;
 
 void RPCServerSignals::OnStarted(std::function<void()> slot) {
     g_rpcSignals.Started.connect(slot);
 }
 
 void RPCServerSignals::OnStopped(std::function<void()> slot) {
     g_rpcSignals.Stopped.connect(slot);
 }
 
 std::string CRPCTable::help(Config &config, const std::string &strCommand,
                             const JSONRPCRequest &helpreq) const {
     std::string strRet;
     std::string category;
     std::set<intptr_t> setDone;
     std::vector<std::pair<std::string, const CRPCCommand *>> vCommands;
 
     for (const auto &entry : mapCommands) {
         vCommands.push_back(
             std::make_pair(entry.second.front()->category + entry.first,
                            entry.second.front()));
     }
     sort(vCommands.begin(), vCommands.end());
 
     JSONRPCRequest jreq(helpreq);
     jreq.fHelp = true;
     jreq.params = UniValue();
 
     for (const std::pair<std::string, const CRPCCommand *> &command :
          vCommands) {
         const CRPCCommand *pcmd = command.second;
         std::string strMethod = pcmd->name;
         if ((strCommand != "" || pcmd->category == "hidden") &&
             strMethod != strCommand) {
             continue;
         }
 
         jreq.strMethod = strMethod;
         try {
             UniValue unused_result;
             if (setDone.insert(pcmd->unique_id).second) {
                 pcmd->actor(config, jreq, unused_result,
                             true /* last_handler */);
             }
         } catch (const std::exception &e) {
             // Help text is returned in an exception
             std::string strHelp = std::string(e.what());
             if (strCommand == "") {
                 if (strHelp.find('\n') != std::string::npos) {
                     strHelp = strHelp.substr(0, strHelp.find('\n'));
                 }
 
                 if (category != pcmd->category) {
                     if (!category.empty()) {
                         strRet += "\n";
                     }
                     category = pcmd->category;
                     strRet += "== " + Capitalize(category) + " ==\n";
                 }
             }
             strRet += strHelp + "\n";
         }
     }
     if (strRet == "") {
         strRet = strprintf("help: unknown command: %s\n", strCommand);
     }
 
     strRet = strRet.substr(0, strRet.size() - 1);
     return strRet;
 }
 
 static UniValue help(Config &config, const JSONRPCRequest &jsonRequest) {
     if (jsonRequest.fHelp || jsonRequest.params.size() > 1) {
         throw std::runtime_error(RPCHelpMan{
             "help",
             "\nList all commands, or get help for a specified command.\n",
             {
-                {"command", RPCArg::Type::STR, /* opt */ true,
-                 /* default_val */ "all commands",
+                {"command", RPCArg::Type::STR, /* default */ "all commands",
                  "The command to get help on"},
             },
             RPCResult{"\"text\"     (string) The help text\n"},
             RPCExamples{""},
         }
                                      .ToString());
     }
 
     std::string strCommand;
     if (jsonRequest.params.size() > 0) {
         strCommand = jsonRequest.params[0].get_str();
     }
 
     return tableRPC.help(config, strCommand, jsonRequest);
 }
 
 static UniValue stop(const Config &config, const JSONRPCRequest &jsonRequest) {
     // Accept the deprecated and ignored 'detach' boolean argument
     // Also accept the hidden 'wait' integer argument (milliseconds)
     // For instance, 'stop 1000' makes the call wait 1 second before returning
     // to the client (intended for testing)
     if (jsonRequest.fHelp || jsonRequest.params.size() > 1) {
         throw std::runtime_error(RPCHelpMan{
             "stop",
             "\nStop Bitcoin server.",
             {},
             RPCResults{},
             RPCExamples{""},
         }
                                      .ToString());
     }
 
     // Event loop will exit after current HTTP requests have been handled, so
     // this reply will get back to the client.
     StartShutdown();
     if (jsonRequest.params[0].isNum()) {
         MilliSleep(jsonRequest.params[0].get_int());
     }
     return "Bitcoin server stopping";
 }
 
 static UniValue uptime(const Config &config,
                        const JSONRPCRequest &jsonRequest) {
     if (jsonRequest.fHelp || jsonRequest.params.size() > 0) {
         throw std::runtime_error(RPCHelpMan{
             "uptime",
             "\nReturns the total uptime of the server.\n",
             {},
             RPCResult{"ttt        (numeric) The number of seconds that the "
                       "server has been running\n"},
             RPCExamples{HelpExampleCli("uptime", "") +
                         HelpExampleRpc("uptime", "")},
         }
                                      .ToString());
     }
 
     return GetTime() - GetStartupTime();
 }
 
 static UniValue getrpcinfo(const Config &config,
                            const JSONRPCRequest &request) {
     if (request.fHelp || request.params.size() > 0) {
         throw std::runtime_error(RPCHelpMan{
             "getrpcinfo",
             "\nReturns details of the RPC server.\n",
             {},
             RPCResults{},
             RPCExamples{""},
         }
                                      .ToString());
     }
 
     LOCK(g_rpc_server_info.mutex);
     UniValue active_commands(UniValue::VARR);
     for (const RPCCommandExecutionInfo &info :
          g_rpc_server_info.active_commands) {
         UniValue entry(UniValue::VOBJ);
         entry.pushKV("method", info.method);
         entry.pushKV("duration", GetTimeMicros() - info.start);
         active_commands.push_back(entry);
     }
 
     UniValue result(UniValue::VOBJ);
     result.pushKV("active_commands", active_commands);
 
     return result;
 }
 
 // clang-format off
 static const CRPCCommand vRPCCommands[] = {
     //  category            name                      actor (function)        argNames
     //  ------------------- ------------------------  ----------------------  ----------
     /* Overall control/query calls */
     { "control",            "getrpcinfo",             getrpcinfo,             {}  },
     { "control",            "help",                   help,                   {"command"}  },
     { "control",            "stop",                   stop,                   {"wait"}  },
     { "control",            "uptime",                 uptime,                 {}  },
 };
 // clang-format on
 
 CRPCTable::CRPCTable() {
     unsigned int vcidx;
     for (vcidx = 0; vcidx < (sizeof(vRPCCommands) / sizeof(vRPCCommands[0]));
          vcidx++) {
         const CRPCCommand *pcmd;
 
         pcmd = &vRPCCommands[vcidx];
         mapCommands[pcmd->name].push_back(pcmd);
     }
 }
 
 bool CRPCTable::appendCommand(const std::string &name,
                               const CRPCCommand *pcmd) {
     if (IsRPCRunning()) {
         return false;
     }
 
     mapCommands[name].push_back(pcmd);
     return true;
 }
 
 bool CRPCTable::removeCommand(const std::string &name,
                               const CRPCCommand *pcmd) {
     auto it = mapCommands.find(name);
     if (it != mapCommands.end()) {
         auto new_end = std::remove(it->second.begin(), it->second.end(), pcmd);
         if (it->second.end() != new_end) {
             it->second.erase(new_end, it->second.end());
             return true;
         }
     }
     return false;
 }
 
 void StartRPC() {
     LogPrint(BCLog::RPC, "Starting RPC\n");
     g_rpc_running = true;
     g_rpcSignals.Started();
 }
 
 void InterruptRPC() {
     LogPrint(BCLog::RPC, "Interrupting RPC\n");
     // Interrupt e.g. running longpolls
     g_rpc_running = false;
 }
 
 void StopRPC() {
     LogPrint(BCLog::RPC, "Stopping RPC\n");
     deadlineTimers.clear();
     DeleteAuthCookie();
     g_rpcSignals.Stopped();
 }
 
 bool IsRPCRunning() {
     return g_rpc_running;
 }
 
 void SetRPCWarmupStatus(const std::string &newStatus) {
     LOCK(cs_rpcWarmup);
     rpcWarmupStatus = newStatus;
 }
 
 void SetRPCWarmupFinished() {
     LOCK(cs_rpcWarmup);
     assert(fRPCInWarmup);
     fRPCInWarmup = false;
 }
 
 bool RPCIsInWarmup(std::string *outStatus) {
     LOCK(cs_rpcWarmup);
     if (outStatus) {
         *outStatus = rpcWarmupStatus;
     }
     return fRPCInWarmup;
 }
 
 bool IsDeprecatedRPCEnabled(ArgsManager &args, const std::string &method) {
     const std::vector<std::string> enabled_methods =
         args.GetArgs("-deprecatedrpc");
 
     return find(enabled_methods.begin(), enabled_methods.end(), method) !=
            enabled_methods.end();
 }
 
 static UniValue JSONRPCExecOne(Config &config, RPCServer &rpcServer,
                                JSONRPCRequest jreq, const UniValue &req) {
     UniValue rpc_result(UniValue::VOBJ);
 
     try {
         jreq.parse(req);
 
         UniValue result = rpcServer.ExecuteCommand(config, jreq);
         rpc_result = JSONRPCReplyObj(result, NullUniValue, jreq.id);
     } catch (const UniValue &objError) {
         rpc_result = JSONRPCReplyObj(NullUniValue, objError, jreq.id);
     } catch (const std::exception &e) {
         rpc_result = JSONRPCReplyObj(
             NullUniValue, JSONRPCError(RPC_PARSE_ERROR, e.what()), jreq.id);
     }
 
     return rpc_result;
 }
 
 std::string JSONRPCExecBatch(Config &config, RPCServer &rpcServer,
                              const JSONRPCRequest &jreq, const UniValue &vReq) {
     UniValue ret(UniValue::VARR);
     for (size_t i = 0; i < vReq.size(); i++) {
         ret.push_back(JSONRPCExecOne(config, rpcServer, jreq, vReq[i]));
     }
 
     return ret.write() + "\n";
 }
 
 /**
  * Process named arguments into a vector of positional arguments, based on the
  * passed-in specification for the RPC call's arguments.
  */
 static inline JSONRPCRequest
 transformNamedArguments(const JSONRPCRequest &in,
                         const std::vector<std::string> &argNames) {
     JSONRPCRequest out = in;
     out.params = UniValue(UniValue::VARR);
     // Build a map of parameters, and remove ones that have been processed, so
     // that we can throw a focused error if there is an unknown one.
     const std::vector<std::string> &keys = in.params.getKeys();
     const std::vector<UniValue> &values = in.params.getValues();
     std::unordered_map<std::string, const UniValue *> argsIn;
     for (size_t i = 0; i < keys.size(); ++i) {
         argsIn[keys[i]] = &values[i];
     }
     // Process expected parameters.
     int hole = 0;
     for (const std::string &argNamePattern : argNames) {
         std::vector<std::string> vargNames;
         boost::algorithm::split(vargNames, argNamePattern,
                                 boost::algorithm::is_any_of("|"));
         auto fr = argsIn.end();
         for (const std::string &argName : vargNames) {
             fr = argsIn.find(argName);
             if (fr != argsIn.end()) {
                 break;
             }
         }
         if (fr != argsIn.end()) {
             for (int i = 0; i < hole; ++i) {
                 // Fill hole between specified parameters with JSON nulls, but
                 // not at the end (for backwards compatibility with calls that
                 // act based on number of specified parameters).
                 out.params.push_back(UniValue());
             }
             hole = 0;
             out.params.push_back(*fr->second);
             argsIn.erase(fr);
         } else {
             hole += 1;
         }
     }
     // If there are still arguments in the argsIn map, this is an error.
     if (!argsIn.empty()) {
         throw JSONRPCError(RPC_INVALID_PARAMETER,
                            "Unknown named parameter " + argsIn.begin()->first);
     }
     // Return request with named arguments transformed to positional arguments
     return out;
 }
 
 UniValue CRPCTable::execute(Config &config,
                             const JSONRPCRequest &request) const {
     // Return immediately if in warmup
     {
         LOCK(cs_rpcWarmup);
         if (fRPCInWarmup) {
             throw JSONRPCError(RPC_IN_WARMUP, rpcWarmupStatus);
         }
     }
 
     // Find method
     auto it = mapCommands.find(request.strMethod);
     if (it != mapCommands.end()) {
         UniValue result;
         for (const auto &command : it->second) {
             if (ExecuteCommand(config, *command, request, result,
                                &command == &it->second.back())) {
                 return result;
             }
         }
     }
     throw JSONRPCError(RPC_METHOD_NOT_FOUND, "Method not found");
 }
 
 static bool ExecuteCommand(Config &config, const CRPCCommand &command,
                            const JSONRPCRequest &request, UniValue &result,
                            bool last_handler) {
     try {
         RPCCommandExecution execution(request.strMethod);
         // Execute, convert arguments to array if necessary
         if (request.params.isObject()) {
             return command.actor(
                 config, transformNamedArguments(request, command.argNames),
                 result, last_handler);
         } else {
             return command.actor(config, request, result, last_handler);
         }
     } catch (const std::exception &e) {
         throw JSONRPCError(RPC_MISC_ERROR, e.what());
     }
 }
 
 std::vector<std::string> CRPCTable::listCommands() const {
     std::vector<std::string> commandList;
     for (const auto &i : mapCommands) {
         commandList.emplace_back(i.first);
     }
     return commandList;
 }
 
 void RPCSetTimerInterfaceIfUnset(RPCTimerInterface *iface) {
     if (!timerInterface) {
         timerInterface = iface;
     }
 }
 
 void RPCSetTimerInterface(RPCTimerInterface *iface) {
     timerInterface = iface;
 }
 
 void RPCUnsetTimerInterface(RPCTimerInterface *iface) {
     if (timerInterface == iface) {
         timerInterface = nullptr;
     }
 }
 
 void RPCRunLater(const std::string &name, std::function<void()> func,
                  int64_t nSeconds) {
     if (!timerInterface) {
         throw JSONRPCError(RPC_INTERNAL_ERROR,
                            "No timer handler registered for RPC");
     }
     deadlineTimers.erase(name);
     LogPrint(BCLog::RPC, "queue run of timer %s in %i seconds (using %s)\n",
              name, nSeconds, timerInterface->Name());
     deadlineTimers.emplace(
         name, std::unique_ptr<RPCTimerBase>(
                   timerInterface->NewTimer(func, nSeconds * 1000)));
 }
 
 int RPCSerializationFlags() {
     return 0;
 }
 
 CRPCTable tableRPC;
diff --git a/src/rpc/util.cpp b/src/rpc/util.cpp
index bb8233838..718ab4108 100644
--- a/src/rpc/util.cpp
+++ b/src/rpc/util.cpp
@@ -1,638 +1,641 @@
 // Copyright (c) 2017 The Bitcoin Core developers
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
 #include <key_io.h>
 #include <keystore.h>
 #include <pubkey.h>
 #include <rpc/protocol.h>
 #include <rpc/util.h>
 #include <tinyformat.h>
 #include <util/strencodings.h>
 
 #include <univalue.h>
 
 #include <boost/variant/static_visitor.hpp>
 
 NodeContext *g_rpc_node = nullptr;
 
 void RPCTypeCheck(const UniValue &params,
                   const std::list<UniValueType> &typesExpected,
                   bool fAllowNull) {
     unsigned int i = 0;
     for (const UniValueType &t : typesExpected) {
         if (params.size() <= i) {
             break;
         }
 
         const UniValue &v = params[i];
         if (!(fAllowNull && v.isNull())) {
             RPCTypeCheckArgument(v, t);
         }
         i++;
     }
 }
 
 void RPCTypeCheckArgument(const UniValue &value,
                           const UniValueType &typeExpected) {
     if (!typeExpected.typeAny && value.type() != typeExpected.type) {
         throw JSONRPCError(RPC_TYPE_ERROR,
                            strprintf("Expected type %s, got %s",
                                      uvTypeName(typeExpected.type),
                                      uvTypeName(value.type())));
     }
 }
 
 void RPCTypeCheckObj(const UniValue &o,
                      const std::map<std::string, UniValueType> &typesExpected,
                      bool fAllowNull, bool fStrict) {
     for (const auto &t : typesExpected) {
         const UniValue &v = find_value(o, t.first);
         if (!fAllowNull && v.isNull()) {
             throw JSONRPCError(RPC_TYPE_ERROR,
                                strprintf("Missing %s", t.first));
         }
 
         if (!(t.second.typeAny || v.type() == t.second.type ||
               (fAllowNull && v.isNull()))) {
             std::string err = strprintf("Expected type %s for %s, got %s",
                                         uvTypeName(t.second.type), t.first,
                                         uvTypeName(v.type()));
             throw JSONRPCError(RPC_TYPE_ERROR, err);
         }
     }
 
     if (fStrict) {
         for (const std::string &k : o.getKeys()) {
             if (typesExpected.count(k) == 0) {
                 std::string err = strprintf("Unexpected key %s", k);
                 throw JSONRPCError(RPC_TYPE_ERROR, err);
             }
         }
     }
 }
 
 Amount AmountFromValue(const UniValue &value) {
     if (!value.isNum() && !value.isStr()) {
         throw JSONRPCError(RPC_TYPE_ERROR, "Amount is not a number or string");
     }
 
     int64_t n;
     if (!ParseFixedPoint(value.getValStr(), 8, &n)) {
         throw JSONRPCError(RPC_TYPE_ERROR, "Invalid amount");
     }
 
     Amount amt = n * SATOSHI;
     if (!MoneyRange(amt)) {
         throw JSONRPCError(RPC_TYPE_ERROR, "Amount out of range");
     }
 
     return amt;
 }
 
 uint256 ParseHashV(const UniValue &v, std::string strName) {
     std::string strHex(v.get_str());
     if (64 != strHex.length()) {
         throw JSONRPCError(
             RPC_INVALID_PARAMETER,
             strprintf("%s must be of length %d (not %d, for '%s')", strName, 64,
                       strHex.length(), strHex));
     }
     // Note: IsHex("") is false
     if (!IsHex(strHex)) {
         throw JSONRPCError(RPC_INVALID_PARAMETER,
                            strName + " must be hexadecimal string (not '" +
                                strHex + "')");
     }
     return uint256S(strHex);
 }
 
 uint256 ParseHashO(const UniValue &o, std::string strKey) {
     return ParseHashV(find_value(o, strKey), strKey);
 }
 
 std::vector<uint8_t> ParseHexV(const UniValue &v, std::string strName) {
     std::string strHex;
     if (v.isStr()) {
         strHex = v.get_str();
     }
     if (!IsHex(strHex)) {
         throw JSONRPCError(RPC_INVALID_PARAMETER,
                            strName + " must be hexadecimal string (not '" +
                                strHex + "')");
     }
 
     return ParseHex(strHex);
 }
 
 std::vector<uint8_t> ParseHexO(const UniValue &o, std::string strKey) {
     return ParseHexV(find_value(o, strKey), strKey);
 }
 
 std::string HelpExampleCli(const std::string &methodname,
                            const std::string &args) {
     return "> bitcoin-cli " + methodname + " " + args + "\n";
 }
 
 std::string HelpExampleRpc(const std::string &methodname,
                            const std::string &args) {
     return "> curl --user myusername --data-binary '{\"jsonrpc\": \"1.0\", "
            "\"id\":\"curltest\", "
            "\"method\": \"" +
            methodname + "\", \"params\": [" + args +
            "] }' -H 'content-type: text/plain;' http://127.0.0.1:8332/\n";
 }
 
 // Converts a hex string to a public key if possible
 CPubKey HexToPubKey(const std::string &hex_in) {
     if (!IsHex(hex_in)) {
         throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY,
                            "Invalid public key: " + hex_in);
     }
     CPubKey vchPubKey(ParseHex(hex_in));
     if (!vchPubKey.IsFullyValid()) {
         throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY,
                            "Invalid public key: " + hex_in);
     }
     return vchPubKey;
 }
 
 // Retrieves a public key for an address from the given CKeyStore
 CPubKey AddrToPubKey(const CChainParams &chainparams, CKeyStore *const keystore,
                      const std::string &addr_in) {
     CTxDestination dest = DecodeDestination(addr_in, chainparams);
     if (!IsValidDestination(dest)) {
         throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY,
                            "Invalid address: " + addr_in);
     }
     CKeyID key = GetKeyForDestination(*keystore, dest);
     if (key.IsNull()) {
         throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY,
                            strprintf("%s does not refer to a key", addr_in));
     }
     CPubKey vchPubKey;
     if (!keystore->GetPubKey(key, vchPubKey)) {
         throw JSONRPCError(
             RPC_INVALID_ADDRESS_OR_KEY,
             strprintf("no full public key for address %s", addr_in));
     }
     if (!vchPubKey.IsFullyValid()) {
         throw JSONRPCError(RPC_INTERNAL_ERROR,
                            "Wallet contains an invalid public key");
     }
     return vchPubKey;
 }
 
 // Creates a multisig redeemscript from a given list of public keys and number
 // required.
 CScript CreateMultisigRedeemscript(const int required,
                                    const std::vector<CPubKey> &pubkeys) {
     // Gather public keys
     if (required < 1) {
         throw JSONRPCError(
             RPC_INVALID_PARAMETER,
             "a multisignature address must require at least one key to redeem");
     }
     if ((int)pubkeys.size() < required) {
         throw JSONRPCError(RPC_INVALID_PARAMETER,
                            strprintf("not enough keys supplied (got %u keys, "
                                      "but need at least %d to redeem)",
                                      pubkeys.size(), required));
     }
     if (pubkeys.size() > 16) {
         throw JSONRPCError(RPC_INVALID_PARAMETER,
                            "Number of keys involved in the multisignature "
                            "address creation > 16\nReduce the number");
     }
 
     CScript result = GetScriptForMultisig(required, pubkeys);
 
     if (result.size() > MAX_SCRIPT_ELEMENT_SIZE) {
         throw JSONRPCError(
             RPC_INVALID_PARAMETER,
             (strprintf("redeemScript exceeds size limit: %d > %d",
                        result.size(), MAX_SCRIPT_ELEMENT_SIZE)));
     }
 
     return result;
 }
 
 class DescribeAddressVisitor : public boost::static_visitor<UniValue> {
 public:
     explicit DescribeAddressVisitor() {}
 
     UniValue operator()(const CNoDestination &dest) const {
         return UniValue(UniValue::VOBJ);
     }
 
     UniValue operator()(const CKeyID &keyID) const {
         UniValue obj(UniValue::VOBJ);
         obj.pushKV("isscript", false);
         return obj;
     }
 
     UniValue operator()(const CScriptID &scriptID) const {
         UniValue obj(UniValue::VOBJ);
         obj.pushKV("isscript", true);
         return obj;
     }
 };
 
 UniValue DescribeAddress(const CTxDestination &dest) {
     return boost::apply_visitor(DescribeAddressVisitor(), dest);
 }
 
 RPCErrorCode RPCErrorFromTransactionError(TransactionError terr) {
     switch (terr) {
         case TransactionError::MEMPOOL_REJECTED:
             return RPC_TRANSACTION_REJECTED;
         case TransactionError::ALREADY_IN_CHAIN:
             return RPC_TRANSACTION_ALREADY_IN_CHAIN;
         case TransactionError::P2P_DISABLED:
             return RPC_CLIENT_P2P_DISABLED;
         case TransactionError::INVALID_PSBT:
         case TransactionError::PSBT_MISMATCH:
             return RPC_INVALID_PARAMETER;
         case TransactionError::SIGHASH_MISMATCH:
             return RPC_DESERIALIZATION_ERROR;
         default:
             break;
     }
     return RPC_TRANSACTION_ERROR;
 }
 
 UniValue JSONRPCTransactionError(TransactionError terr,
                                  const std::string &err_string) {
     if (err_string.length() > 0) {
         return JSONRPCError(RPCErrorFromTransactionError(terr), err_string);
     } else {
         return JSONRPCError(RPCErrorFromTransactionError(terr),
                             TransactionErrorString(terr));
     }
 }
 
 struct Section {
     Section(const std::string &left, const std::string &right)
         : m_left{left}, m_right{right} {}
     const std::string m_left;
     const std::string m_right;
 };
 
 struct Sections {
     std::vector<Section> m_sections;
     size_t m_max_pad{0};
 
     void PushSection(const Section &s) {
         m_max_pad = std::max(m_max_pad, s.m_left.size());
         m_sections.push_back(s);
     }
 
     enum class OuterType {
         ARR,
         OBJ,
         // Only set on first recursion
         NAMED_ARG,
     };
 
     void Push(const RPCArg &arg, const size_t current_indent = 5,
               const OuterType outer_type = OuterType::NAMED_ARG) {
         const auto indent = std::string(current_indent, ' ');
         const auto indent_next = std::string(current_indent + 2, ' ');
         switch (arg.m_type) {
             case RPCArg::Type::STR_HEX:
             case RPCArg::Type::STR:
             case RPCArg::Type::NUM:
             case RPCArg::Type::AMOUNT:
             case RPCArg::Type::BOOL: {
                 // Nothing more to do for non-recursive types on first recursion
                 if (outer_type == OuterType::NAMED_ARG) {
                     return;
                 }
                 auto left = indent;
                 if (arg.m_type_str.size() != 0 &&
                     outer_type == OuterType::OBJ) {
                     left += "\"" + arg.m_name + "\": " + arg.m_type_str.at(0);
                 } else {
                     left += outer_type == OuterType::OBJ
                                 ? arg.ToStringObj(/* oneline */ false)
                                 : arg.ToString(/* oneline */ false);
                 }
                 left += ",";
-                PushSection({left, arg.ToDescriptionString(
-                                       /* implicitly_required */ outer_type ==
-                                       OuterType::ARR)});
+                PushSection({left, arg.ToDescriptionString()});
                 break;
             }
             case RPCArg::Type::OBJ:
             case RPCArg::Type::OBJ_USER_KEYS: {
-                const auto right =
-                    outer_type == OuterType::NAMED_ARG
-                        ? ""
-                        : arg.ToDescriptionString(
-                              /* implicitly_required */ outer_type ==
-                              OuterType::ARR);
+                const auto right = outer_type == OuterType::NAMED_ARG
+                                       ? ""
+                                       : arg.ToDescriptionString();
                 PushSection({indent + "{", right});
                 for (const auto &arg_inner : arg.m_inner) {
                     Push(arg_inner, current_indent + 2, OuterType::OBJ);
                 }
                 if (arg.m_type != RPCArg::Type::OBJ) {
                     PushSection({indent_next + "...", ""});
                 }
                 PushSection(
                     {indent + "}" +
                          (outer_type != OuterType::NAMED_ARG ? "," : ""),
                      ""});
                 break;
             }
             case RPCArg::Type::ARR: {
                 auto left = indent;
                 left += outer_type == OuterType::OBJ
                             ? "\"" + arg.m_name + "\": "
                             : "";
                 left += "[";
-                const auto right =
-                    outer_type == OuterType::NAMED_ARG
-                        ? ""
-                        : arg.ToDescriptionString(
-                              /* implicitly_required */ outer_type ==
-                              OuterType::ARR);
+                const auto right = outer_type == OuterType::NAMED_ARG
+                                       ? ""
+                                       : arg.ToDescriptionString();
                 PushSection({left, right});
                 for (const auto &arg_inner : arg.m_inner) {
                     Push(arg_inner, current_indent + 2, OuterType::ARR);
                 }
                 PushSection({indent_next + "...", ""});
                 PushSection(
                     {indent + "]" +
                          (outer_type != OuterType::NAMED_ARG ? "," : ""),
                      ""});
                 break;
             }
 
                 // no default case, so the compiler can warn about missing cases
         }
     }
 
     std::string ToString() const {
         std::string ret;
         const size_t pad = m_max_pad + 4;
         for (const auto &s : m_sections) {
             if (s.m_right.empty()) {
                 ret += s.m_left;
                 ret += "\n";
                 continue;
             }
 
             std::string left = s.m_left;
             left.resize(pad, ' ');
             ret += left;
 
             // Properly pad after newlines
             std::string right;
             size_t begin = 0;
             size_t new_line_pos = s.m_right.find_first_of('\n');
             while (true) {
                 right += s.m_right.substr(begin, new_line_pos - begin);
                 if (new_line_pos == std::string::npos) {
                     // No new line
                     break;
                 }
                 right += "\n" + std::string(pad, ' ');
                 begin = s.m_right.find_first_not_of(' ', new_line_pos + 1);
                 if (begin == std::string::npos) {
                     break; // Empty line
                 }
                 new_line_pos = s.m_right.find_first_of('\n', begin + 1);
             }
             ret += right;
             ret += "\n";
         }
         return ret;
     }
 };
 
 RPCHelpMan::RPCHelpMan(std::string name, std::string description,
                        std::vector<RPCArg> args, RPCResults results,
                        RPCExamples examples)
     : m_name{std::move(name)}, m_description{std::move(description)},
       m_args{std::move(args)}, m_results{std::move(results)},
       m_examples{std::move(examples)} {
     std::set<std::string> named_args;
     for (const auto &arg : m_args) {
         // Should have unique named arguments
         CHECK_NONFATAL(named_args.insert(arg.m_name).second);
     }
 }
 
 std::string RPCResults::ToDescriptionString() const {
     std::string result;
     for (const auto &r : m_results) {
         if (r.m_cond.empty()) {
             result += "\nResult:\n";
         } else {
             result += "\nResult (" + r.m_cond + "):\n";
         }
         result += r.m_result;
     }
     return result;
 }
 
 std::string RPCExamples::ToDescriptionString() const {
     return m_examples.empty() ? m_examples : "\nExamples:\n" + m_examples;
 }
 
 std::string RPCHelpMan::ToString() const {
     std::string ret;
 
     // Oneline summary
     ret += m_name;
     bool was_optional{false};
     for (const auto &arg : m_args) {
+        bool optional;
+        if (arg.m_fallback.which() == 1) {
+            optional = true;
+        } else {
+            optional = RPCArg::Optional::NO !=
+                       boost::get<RPCArg::Optional>(arg.m_fallback);
+        }
         ret += " ";
-        if (arg.m_optional) {
+        if (optional) {
             if (!was_optional) {
                 ret += "( ";
             }
             was_optional = true;
         } else {
             if (was_optional) {
                 ret += ") ";
             }
             was_optional = false;
         }
         ret += arg.ToString(/* oneline */ true);
     }
     if (was_optional) {
         ret += " )";
     }
     ret += "\n";
 
     // Description
     ret += m_description;
 
     // Arguments
     Sections sections;
     for (size_t i{0}; i < m_args.size(); ++i) {
         const auto &arg = m_args.at(i);
 
         if (i == 0) {
             ret += "\nArguments:\n";
         }
 
         // Push named argument name and description
         sections.m_sections.emplace_back(std::to_string(i + 1) + ". " +
                                              arg.m_name,
                                          arg.ToDescriptionString());
         sections.m_max_pad = std::max(sections.m_max_pad,
                                       sections.m_sections.back().m_left.size());
 
         // Recursively push nested args
         sections.Push(arg);
     }
     ret += sections.ToString();
 
     // Result
     ret += m_results.ToDescriptionString();
 
     // Examples
     ret += m_examples.ToDescriptionString();
 
     return ret;
 }
 
-std::string RPCArg::ToDescriptionString(const bool implicitly_required) const {
+std::string RPCArg::ToDescriptionString() const {
     std::string ret;
     ret += "(";
     if (m_type_str.size() != 0) {
         ret += m_type_str.at(1);
     } else {
         switch (m_type) {
             case Type::STR_HEX:
             case Type::STR: {
                 ret += "string";
                 break;
             }
             case Type::NUM: {
                 ret += "numeric";
                 break;
             }
             case Type::AMOUNT: {
                 ret += "numeric or string";
                 break;
             }
             case Type::BOOL: {
                 ret += "boolean";
                 break;
             }
             case Type::OBJ:
             case Type::OBJ_USER_KEYS: {
                 ret += "json object";
                 break;
             }
             case Type::ARR: {
                 ret += "json array";
                 break;
             }
 
                 // no default case, so the compiler can warn about missing cases
         }
     }
-    if (!implicitly_required) {
-        ret += ", ";
-        if (m_optional) {
-            ret += "optional";
-            if (!m_default_value.empty()) {
-                ret += ", default=" + m_default_value;
-            } else {
-                // TODO enable this assert, when all optional parameters have
-                // their default value documented
-                // assert(false);
+    if (m_fallback.which() == 1) {
+        ret += ", optional, default=" + boost::get<std::string>(m_fallback);
+    } else {
+        switch (boost::get<RPCArg::Optional>(m_fallback)) {
+            case RPCArg::Optional::OMITTED: {
+                // nothing to do. Element is treated as if not present and has
+                // no default value
+                break;
             }
-        } else {
-            ret += "required";
-            // Default value is ignored, and must not be present
-            assert(m_default_value.empty());
+            case RPCArg::Optional::OMITTED_NAMED_ARG: {
+                ret += ", optional"; // Default value is "null"
+                break;
+            }
+            case RPCArg::Optional::NO: {
+                ret += ", required";
+                break;
+            }
+
+                // no default case, so the compiler can warn about missing cases
         }
     }
     ret += ")";
     ret += m_description.empty() ? "" : " " + m_description;
     return ret;
 }
 
 std::string RPCArg::ToStringObj(const bool oneline) const {
     std::string res;
     res += "\"";
     res += m_name;
     if (oneline) {
         res += "\":";
     } else {
         res += "\": ";
     }
     switch (m_type) {
         case Type::STR:
             return res + "\"str\"";
         case Type::STR_HEX:
             return res + "\"hex\"";
         case Type::NUM:
             return res + "n";
         case Type::AMOUNT:
             return res + "amount";
         case Type::BOOL:
             return res + "bool";
         case Type::ARR:
             res += "[";
             for (const auto &i : m_inner) {
                 res += i.ToString(oneline) + ",";
             }
             return res + "...]";
         case Type::OBJ:
         case Type::OBJ_USER_KEYS:
             // Currently unused, so avoid writing dead code
             assert(false);
 
             // no default case, so the compiler can warn about missing cases
     }
     assert(false);
 }
 
 std::string RPCArg::ToString(const bool oneline) const {
     if (oneline && !m_oneline_description.empty()) {
         return m_oneline_description;
     }
 
     switch (m_type) {
         case Type::STR_HEX:
         case Type::STR: {
             return "\"" + m_name + "\"";
         }
         case Type::NUM:
         case Type::AMOUNT:
         case Type::BOOL: {
             return m_name;
         }
         case Type::OBJ:
         case Type::OBJ_USER_KEYS: {
             std::string res;
             for (size_t i = 0; i < m_inner.size();) {
                 res += m_inner[i].ToStringObj(oneline);
                 if (++i < m_inner.size()) {
                     res += ",";
                 }
             }
             if (m_type == Type::OBJ) {
                 return "{" + res + "}";
             } else {
                 return "{" + res + ",...}";
             }
         }
         case Type::ARR: {
             std::string res;
             for (const auto &i : m_inner) {
                 res += i.ToString(oneline) + ",";
             }
             return "[" + res + "...]";
         }
 
             // no default case, so the compiler can warn about missing cases
     }
     assert(false);
 }
diff --git a/src/rpc/util.h b/src/rpc/util.h
index c82a4f74a..38cd49c88 100644
--- a/src/rpc/util.h
+++ b/src/rpc/util.h
@@ -1,219 +1,238 @@
 // Copyright (c) 2017 The Bitcoin Core developers
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
 #ifndef BITCOIN_RPC_UTIL_H
 #define BITCOIN_RPC_UTIL_H
 
 #include <node/transaction.h>
 #include <rpc/protocol.h>
 #include <script/standard.h> // For CTxDestination
 #include <univalue.h>
 #include <util/check.h>
 
+#include <boost/variant.hpp>
+
 #include <string>
 #include <vector>
 
 class CChainParams;
 class CKeyStore;
 class CPubKey;
 class CScript;
 struct NodeContext;
 class UniValue;
 
 //! Pointers to interfaces that need to be accessible from RPC methods. Due to
 //! limitations of the RPC framework, there's currently no direct way to pass in
 //! state to RPC method implementations.
 extern NodeContext *g_rpc_node;
 
 /**
  * Wrapper for UniValue::VType, which includes typeAny: used to denote don't
  * care type.
  */
 struct UniValueType {
     UniValueType(UniValue::VType _type) : typeAny(false), type(_type) {}
     UniValueType() : typeAny(true) {}
     bool typeAny;
     UniValue::VType type;
 };
 
 /**
  * Type-check arguments; throws JSONRPCError if wrong type given. Does not check
  * that the right number of arguments are passed, just that any passed are the
  * correct type.
  */
 void RPCTypeCheck(const UniValue &params,
                   const std::list<UniValueType> &typesExpected,
                   bool fAllowNull = false);
 
 /**
  * Type-check one argument; throws JSONRPCError if wrong type given.
  */
 void RPCTypeCheckArgument(const UniValue &value,
                           const UniValueType &typeExpected);
 
 /**
  * Check for expected keys/value types in an Object.
  */
 void RPCTypeCheckObj(const UniValue &o,
                      const std::map<std::string, UniValueType> &typesExpected,
                      bool fAllowNull = false, bool fStrict = false);
 
 /**
  * Utilities: convert hex-encoded values (throws error if not hex).
  */
 extern uint256 ParseHashV(const UniValue &v, std::string strName);
 extern uint256 ParseHashO(const UniValue &o, std::string strKey);
 extern std::vector<uint8_t> ParseHexV(const UniValue &v, std::string strName);
 extern std::vector<uint8_t> ParseHexO(const UniValue &o, std::string strKey);
 
 extern Amount AmountFromValue(const UniValue &value);
 extern std::string HelpExampleCli(const std::string &methodname,
                                   const std::string &args);
 extern std::string HelpExampleRpc(const std::string &methodname,
                                   const std::string &args);
 
 CPubKey HexToPubKey(const std::string &hex_in);
 CPubKey AddrToPubKey(const CChainParams &chainparams, CKeyStore *const keystore,
                      const std::string &addr_in);
 CScript CreateMultisigRedeemscript(const int required,
                                    const std::vector<CPubKey> &pubkeys);
 
 UniValue DescribeAddress(const CTxDestination &dest);
 
 RPCErrorCode RPCErrorFromTransactionError(TransactionError terr);
 UniValue JSONRPCTransactionError(TransactionError terr,
                                  const std::string &err_string = "");
 
 struct RPCArg {
     enum class Type {
         OBJ,
         ARR,
         STR,
         NUM,
         BOOL,
         //! Special type where the user must set the keys e.g. to define
         //! multiple addresses; as opposed to e.g. an options object where the
         //! keys are predefined
         OBJ_USER_KEYS,
         //! Special type representing a floating point amount (can be either NUM
         //! or STR)
         AMOUNT,
         //! Special type that is a STR with only hex chars
         STR_HEX,
     };
+
+    enum class Optional {
+        /** Required arg */
+        NO,
+        /**
+         * Optinal arg that is a named argument and has a default value of
+         * `null`. When possible, the default value should be specified.
+         */
+        OMITTED_NAMED_ARG,
+        /**
+         * Optional argument with default value omitted because they are
+         * implicitly clear. That is, elements in an array or object may not
+         * exist by default.
+         * When possible, the default value should be specified.
+         */
+        OMITTED,
+    };
+    using Fallback =
+        boost::variant<Optional,
+                       /* default value for optional args */ std::string>;
+
     //! The name of the arg (can be empty for inner args)
     const std::string m_name;
     const Type m_type;
     //! Only used for arrays or dicts
     const std::vector<RPCArg> m_inner;
-    const bool m_optional;
-    const std::string m_default_value; //!< Only used for optional args
+    const Fallback m_fallback;
     const std::string m_description;
     //! Should be empty unless it is supposed to override the auto-generated
     //! summary line
     const std::string m_oneline_description;
 
     //! Should be empty unless it is supposed to override the
     //! auto-generated type strings. Vector length is either 0
     //! or 2, m_type_str.at(0) will override the type of the
     //! value in a key-value pair, m_type_str.at(1) will
     //! override the type in the argument description.
     const std::vector<std::string> m_type_str;
 
-    RPCArg(const std::string &name, const Type &type, const bool opt,
-           const std::string &default_val, const std::string &description,
+    RPCArg(const std::string &name, const Type &type, const Fallback &fallback,
+           const std::string &description,
            const std::string &oneline_description = "",
            const std::vector<std::string> &type_str = {})
-        : m_name{name}, m_type{type}, m_optional{opt},
-          m_default_value{default_val}, m_description{description},
+        : m_name{name}, m_type{type}, m_fallback{fallback},
+          m_description{description},
           m_oneline_description{oneline_description}, m_type_str{type_str} {
         CHECK_NONFATAL(type != Type::ARR && type != Type::OBJ);
     }
 
-    RPCArg(const std::string &name, const Type &type, const bool opt,
-           const std::string &default_val, const std::string &description,
-           const std::vector<RPCArg> &inner,
+    RPCArg(const std::string &name, const Type &type, const Fallback &fallback,
+           const std::string &description, const std::vector<RPCArg> &inner,
            const std::string &oneline_description = "",
            const std::vector<std::string> &type_str = {})
-        : m_name{name}, m_type{type}, m_inner{inner}, m_optional{opt},
-          m_default_value{default_val}, m_description{description},
+        : m_name{name}, m_type{type}, m_inner{inner}, m_fallback{fallback},
+          m_description{description},
           m_oneline_description{oneline_description}, m_type_str{type_str} {
         CHECK_NONFATAL(type == Type::ARR || type == Type::OBJ);
     }
 
     /**
      * Return the type string of the argument.
      * Set oneline to allow it to be overridden by a custom oneline type string
      * (m_oneline_description).
      */
     std::string ToString(bool oneline) const;
     /**
      * Return the type string of the argument when it is in an object (dict).
      * Set oneline to get the oneline representation (less whitespace)
      */
     std::string ToStringObj(bool oneline) const;
     /**
      * Return the description string, including the argument type and whether
      * the argument is required.
-     * implicitly_required is set for arguments in an array, which are neither
-     * optional nor required.
      */
-    std::string ToDescriptionString(bool implicitly_required = false) const;
+    std::string ToDescriptionString() const;
 };
 
 struct RPCResult {
     const std::string m_cond;
     const std::string m_result;
 
     explicit RPCResult(std::string result)
         : m_cond{}, m_result{std::move(result)} {
         CHECK_NONFATAL(!m_result.empty());
     }
 
     RPCResult(std::string cond, std::string result)
         : m_cond{std::move(cond)}, m_result{std::move(result)} {
         CHECK_NONFATAL(!m_cond.empty());
         CHECK_NONFATAL(!m_result.empty());
     }
 };
 
 struct RPCResults {
     const std::vector<RPCResult> m_results;
 
     RPCResults() : m_results{} {}
 
     RPCResults(RPCResult result) : m_results{{result}} {}
 
     RPCResults(std::initializer_list<RPCResult> results) : m_results{results} {}
 
     /**
      * Return the description string.
      */
     std::string ToDescriptionString() const;
 };
 
 struct RPCExamples {
     const std::string m_examples;
     RPCExamples(std::string examples) : m_examples(std::move(examples)) {}
     RPCExamples() : m_examples(std::move("")) {}
     std::string ToDescriptionString() const;
 };
 
 class RPCHelpMan {
 public:
     RPCHelpMan(std::string name, std::string description,
                std::vector<RPCArg> args, RPCResults results,
                RPCExamples examples);
 
     std::string ToString() const;
 
 private:
     const std::string m_name;
     const std::string m_description;
     const std::vector<RPCArg> m_args;
     const RPCResults m_results;
     const RPCExamples m_examples;
 };
 
 #endif // BITCOIN_RPC_UTIL_H
diff --git a/src/wallet/rpcdump.cpp b/src/wallet/rpcdump.cpp
index 6d9a847dc..2fe74f44a 100644
--- a/src/wallet/rpcdump.cpp
+++ b/src/wallet/rpcdump.cpp
@@ -1,1896 +1,1875 @@
 // Copyright (c) 2009-2016 The Bitcoin Core developers
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
 #include <chain.h>
 #include <config.h>
 #include <core_io.h>
 #include <interfaces/chain.h>
 #include <key_io.h>
 #include <merkleblock.h>
 #include <rpc/server.h>
 #include <rpc/util.h>
 #include <script/descriptor.h>
 #include <script/script.h>
 #include <script/standard.h>
 #include <sync.h>
 #include <util/system.h>
 #include <util/time.h>
 #include <util/translation.h>
 #include <validation.h>
 #include <wallet/rpcwallet.h>
 #include <wallet/wallet.h>
 
 #include <boost/algorithm/string.hpp>
 
 #include <univalue.h>
 
 #include <cstdint>
 
 static std::string EncodeDumpString(const std::string &str) {
     std::stringstream ret;
     for (const uint8_t c : str) {
         if (c <= 32 || c >= 128 || c == '%') {
             ret << '%' << HexStr(&c, &c + 1);
         } else {
             ret << c;
         }
     }
     return ret.str();
 }
 
 static std::string DecodeDumpString(const std::string &str) {
     std::stringstream ret;
     for (unsigned int pos = 0; pos < str.length(); pos++) {
         uint8_t c = str[pos];
         if (c == '%' && pos + 2 < str.length()) {
             c = (((str[pos + 1] >> 6) * 9 + ((str[pos + 1] - '0') & 15)) << 4) |
                 ((str[pos + 2] >> 6) * 9 + ((str[pos + 2] - '0') & 15));
             pos += 2;
         }
         ret << c;
     }
     return ret.str();
 }
 
 bool GetWalletAddressesForKey(const Config &config, CWallet *const pwallet,
                               const CKeyID &keyid, std::string &strAddr,
                               std::string &strLabel) {
     bool fLabelFound = false;
     CKey key;
     pwallet->GetKey(keyid, key);
     for (const auto &dest : GetAllDestinationsForKey(key.GetPubKey())) {
         if (pwallet->mapAddressBook.count(dest)) {
             if (!strAddr.empty()) {
                 strAddr += ",";
             }
             strAddr += EncodeDestination(dest, config);
             strLabel = EncodeDumpString(pwallet->mapAddressBook[dest].name);
             fLabelFound = true;
         }
     }
     if (!fLabelFound) {
         strAddr = EncodeDestination(
             GetDestinationForKey(key.GetPubKey(),
                                  pwallet->m_default_address_type),
             config);
     }
     return fLabelFound;
 }
 
 static const int64_t TIMESTAMP_MIN = 0;
 
 static void RescanWallet(CWallet &wallet, const WalletRescanReserver &reserver,
                          int64_t time_begin = TIMESTAMP_MIN,
                          bool update = true) {
     int64_t scanned_time = wallet.RescanFromTime(time_begin, reserver, update);
     if (wallet.IsAbortingRescan()) {
         throw JSONRPCError(RPC_MISC_ERROR, "Rescan aborted by user.");
     } else if (scanned_time > time_begin) {
         throw JSONRPCError(RPC_WALLET_ERROR,
                            "Rescan was unable to fully rescan the blockchain. "
                            "Some transactions may be missing.");
     }
 }
 
 UniValue importprivkey(const Config &config, const JSONRPCRequest &request) {
     std::shared_ptr<CWallet> const wallet = GetWalletForJSONRPCRequest(request);
     CWallet *const pwallet = wallet.get();
     if (!EnsureWalletIsAvailable(pwallet, request.fHelp)) {
         return NullUniValue;
     }
 
     if (request.fHelp || request.params.size() < 1 ||
         request.params.size() > 3) {
         throw std::runtime_error(RPCHelpMan{
             "importprivkey",
             "\nAdds a private key (as returned by dumpprivkey) to "
             "your wallet. Requires a new wallet backup.\n"
             "Hint: use importmulti to import more than one private key.\n"
             "\nNote: This call can take minutes to complete if rescan is true, "
             "during that time, other rpc calls\n"
             "may report that the imported key exists but related transactions "
             "are still missing, leading to temporarily incorrect/bogus "
             "balances and unspent outputs until rescan completes.\n",
             {
-                {"privkey", RPCArg::Type::STR, /* opt */ false,
-                 /* default_val */ "", "The private key (see dumpprivkey)"},
-                {"label", RPCArg::Type::STR, /* opt */ true,
-                 /* default_val */
+                {"privkey", RPCArg::Type::STR, RPCArg::Optional::NO,
+                 "The private key (see dumpprivkey)"},
+                {"label", RPCArg::Type::STR, /* default */
                  "current label if address exists, otherwise \"\"",
                  "An optional label"},
-                {"rescan", RPCArg::Type::BOOL, /* opt */ true,
-                 /* default_val */ "true",
+                {"rescan", RPCArg::Type::BOOL, /* default */ "true",
                  "Rescan the wallet for transactions"},
             },
             RPCResults{},
             RPCExamples{
                 "\nDump a private key\n" +
                 HelpExampleCli("dumpprivkey", "\"myaddress\"") +
                 "\nImport the private key with rescan\n" +
                 HelpExampleCli("importprivkey", "\"mykey\"") +
                 "\nImport using a label and without rescan\n" +
                 HelpExampleCli("importprivkey", "\"mykey\" \"testing\" false") +
                 "\nImport using default blank label and without rescan\n" +
                 HelpExampleCli("importprivkey", "\"mykey\" \"\" false") +
                 "\nAs a JSON-RPC call\n" +
                 HelpExampleRpc("importprivkey",
                                "\"mykey\", \"testing\", false")},
         }
                                      .ToString());
     }
 
     if (pwallet->IsWalletFlagSet(WALLET_FLAG_DISABLE_PRIVATE_KEYS)) {
         throw JSONRPCError(RPC_WALLET_ERROR,
                            "Cannot import private keys to a wallet with "
                            "private keys disabled");
     }
 
     WalletRescanReserver reserver(pwallet);
     bool fRescan = true;
     {
         auto locked_chain = pwallet->chain().lock();
         LOCK(pwallet->cs_wallet);
 
         EnsureWalletIsUnlocked(pwallet);
 
         std::string strSecret = request.params[0].get_str();
         std::string strLabel = "";
         if (!request.params[1].isNull()) {
             strLabel = request.params[1].get_str();
         }
 
         // Whether to perform rescan after import
         if (!request.params[2].isNull()) {
             fRescan = request.params[2].get_bool();
         }
 
         if (fRescan && pwallet->chain().getPruneMode()) {
             throw JSONRPCError(RPC_WALLET_ERROR,
                                "Rescan is disabled in pruned mode");
         }
 
         if (fRescan && !reserver.reserve()) {
             throw JSONRPCError(RPC_WALLET_ERROR,
                                "Wallet is currently rescanning. Abort existing "
                                "rescan or wait.");
         }
 
         CKey key = DecodeSecret(strSecret);
         if (!key.IsValid()) {
             throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY,
                                "Invalid private key encoding");
         }
 
         CPubKey pubkey = key.GetPubKey();
         assert(key.VerifyPubKey(pubkey));
         CKeyID vchAddress = pubkey.GetID();
         {
             pwallet->MarkDirty();
 
             // We don't know which corresponding address will be used;
             // label all new addresses, and label existing addresses if a
             // label was passed.
             for (const auto &dest : GetAllDestinationsForKey(pubkey)) {
                 if (!request.params[1].isNull() ||
                     pwallet->mapAddressBook.count(dest) == 0) {
                     pwallet->SetAddressBook(dest, strLabel, "receive");
                 }
             }
 
             // Don't throw error in case a key is already there
             if (pwallet->HaveKey(vchAddress)) {
                 return NullUniValue;
             }
 
             pwallet->LearnAllRelatedScripts(pubkey);
 
             // whenever a key is imported, we need to scan the whole chain
             pwallet->UpdateTimeFirstKey(1);
             pwallet->mapKeyMetadata[vchAddress].nCreateTime = 1;
 
             if (!pwallet->AddKeyPubKey(key, pubkey)) {
                 throw JSONRPCError(RPC_WALLET_ERROR,
                                    "Error adding key to wallet");
             }
         }
     }
     if (fRescan) {
         RescanWallet(*pwallet, reserver);
     }
 
     return NullUniValue;
 }
 
 UniValue abortrescan(const Config &config, const JSONRPCRequest &request) {
     std::shared_ptr<CWallet> const wallet = GetWalletForJSONRPCRequest(request);
     CWallet *const pwallet = wallet.get();
     if (!EnsureWalletIsAvailable(pwallet, request.fHelp)) {
         return NullUniValue;
     }
 
     if (request.fHelp || request.params.size() > 0) {
         throw std::runtime_error(RPCHelpMan{
             "abortrescan",
             "\nStops current wallet rescan triggered by "
             "an RPC call, e.g. by an importprivkey call.\n",
             {},
             RPCResults{},
             RPCExamples{"\nImport a private key\n" +
                         HelpExampleCli("importprivkey", "\"mykey\"") +
                         "\nAbort the running wallet rescan\n" +
                         HelpExampleCli("abortrescan", "") +
                         "\nAs a JSON-RPC call\n" +
                         HelpExampleRpc("abortrescan", "")},
         }
                                      .ToString());
     }
 
     if (!pwallet->IsScanning() || pwallet->IsAbortingRescan()) {
         return false;
     }
     pwallet->AbortRescan();
     return true;
 }
 
 static void ImportAddress(CWallet *, const CTxDestination &dest,
                           const std::string &strLabel);
 static void ImportScript(CWallet *const pwallet, const CScript &script,
                          const std::string &strLabel, bool isRedeemScript)
     EXCLUSIVE_LOCKS_REQUIRED(pwallet->cs_wallet) {
     if (!isRedeemScript && ::IsMine(*pwallet, script) == ISMINE_SPENDABLE) {
         throw JSONRPCError(RPC_WALLET_ERROR, "The wallet already contains the "
                                              "private key for this address or "
                                              "script");
     }
 
     pwallet->MarkDirty();
 
     if (!pwallet->HaveWatchOnly(script) &&
         !pwallet->AddWatchOnly(script, 0 /* nCreateTime */)) {
         throw JSONRPCError(RPC_WALLET_ERROR, "Error adding address to wallet");
     }
 
     if (isRedeemScript) {
         const CScriptID id(script);
         if (!pwallet->HaveCScript(id) && !pwallet->AddCScript(script)) {
             throw JSONRPCError(RPC_WALLET_ERROR,
                                "Error adding p2sh redeemScript to wallet");
         }
         ImportAddress(pwallet, id, strLabel);
     } else {
         CTxDestination destination;
         if (ExtractDestination(script, destination)) {
             pwallet->SetAddressBook(destination, strLabel, "receive");
         }
     }
 }
 
 static void ImportAddress(CWallet *const pwallet, const CTxDestination &dest,
                           const std::string &strLabel)
     EXCLUSIVE_LOCKS_REQUIRED(pwallet->cs_wallet) {
     CScript script = GetScriptForDestination(dest);
     ImportScript(pwallet, script, strLabel, false);
     // add to address book or update label
     if (IsValidDestination(dest)) {
         pwallet->SetAddressBook(dest, strLabel, "receive");
     }
 }
 
 UniValue importaddress(const Config &config, const JSONRPCRequest &request) {
     std::shared_ptr<CWallet> const wallet = GetWalletForJSONRPCRequest(request);
     CWallet *const pwallet = wallet.get();
     if (!EnsureWalletIsAvailable(pwallet, request.fHelp)) {
         return NullUniValue;
     }
 
     if (request.fHelp || request.params.size() < 1 ||
         request.params.size() > 4) {
         throw std::runtime_error(RPCHelpMan{
             "importaddress",
             "\nAdds an address or script (in hex) that can be "
             "watched as if it were in your wallet but cannot be "
             "used to spend. Requires a new wallet backup.\n"
             "\nNote: This call can take minutes to complete if rescan is true, "
             "during that time, other rpc calls\n"
             "may report that the imported address exists but related "
             "transactions are still missing, leading to temporarily "
             "incorrect/bogus balances and unspent outputs until rescan "
             "completes.\n"
             "If you have the full public key, you should call importpubkey "
             "instead of this.\n"
             "\nNote: If you import a non-standard raw script in hex form, "
             "outputs sending to it will be treated\n"
             "as change, and not show up in many RPCs.\n",
             {
-                {"address", RPCArg::Type::STR, /* opt */ false,
-                 /* default_val */ "",
+                {"address", RPCArg::Type::STR, RPCArg::Optional::NO,
                  "The Bitcoin address (or hex-encoded script)"},
-                {"label", RPCArg::Type::STR, /* opt */ true,
-                 /* default_val */ "\"\"", "An optional label"},
-                {"rescan", RPCArg::Type::BOOL, /* opt */ true,
-                 /* default_val */ "true",
+                {"label", RPCArg::Type::STR, /* default */ "\"\"",
+                 "An optional label"},
+                {"rescan", RPCArg::Type::BOOL, /* default */ "true",
                  "Rescan the wallet for transactions"},
-                {"p2sh", RPCArg::Type::BOOL, /* opt */ true,
-                 /* default_val */ "false",
+                {"p2sh", RPCArg::Type::BOOL, /* default */ "false",
                  "Add the P2SH version of the script as well"},
             },
             RPCResults{},
             RPCExamples{"\nImport an address with rescan\n" +
                         HelpExampleCli("importaddress", "\"myaddress\"") +
                         "\nImport using a label without rescan\n" +
                         HelpExampleCli("importaddress",
                                        "\"myaddress\" \"testing\" false") +
                         "\nAs a JSON-RPC call\n" +
                         HelpExampleRpc("importaddress",
                                        "\"myaddress\", \"testing\", false")},
         }
                                      .ToString());
     }
 
     std::string strLabel;
     if (!request.params[1].isNull()) {
         strLabel = request.params[1].get_str();
     }
 
     // Whether to perform rescan after import
     bool fRescan = true;
     if (!request.params[2].isNull()) {
         fRescan = request.params[2].get_bool();
     }
 
     if (fRescan && pwallet->chain().getPruneMode()) {
         throw JSONRPCError(RPC_WALLET_ERROR,
                            "Rescan is disabled in pruned mode");
     }
 
     WalletRescanReserver reserver(pwallet);
     if (fRescan && !reserver.reserve()) {
         throw JSONRPCError(
             RPC_WALLET_ERROR,
             "Wallet is currently rescanning. Abort existing rescan or wait.");
     }
 
     // Whether to import a p2sh version, too
     bool fP2SH = false;
     if (!request.params[3].isNull()) {
         fP2SH = request.params[3].get_bool();
     }
 
     {
         auto locked_chain = pwallet->chain().lock();
         LOCK(pwallet->cs_wallet);
 
         CTxDestination dest = DecodeDestination(request.params[0].get_str(),
                                                 config.GetChainParams());
         if (IsValidDestination(dest)) {
             if (fP2SH) {
                 throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY,
                                    "Cannot use the p2sh flag with an address - "
                                    "use a script instead");
             }
             ImportAddress(pwallet, dest, strLabel);
         } else if (IsHex(request.params[0].get_str())) {
             std::vector<uint8_t> data(ParseHex(request.params[0].get_str()));
             ImportScript(pwallet, CScript(data.begin(), data.end()), strLabel,
                          fP2SH);
         } else {
             throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY,
                                "Invalid Bitcoin address or script");
         }
     }
     if (fRescan) {
         RescanWallet(*pwallet, reserver);
         pwallet->ReacceptWalletTransactions();
     }
 
     return NullUniValue;
 }
 
 UniValue importprunedfunds(const Config &config,
                            const JSONRPCRequest &request) {
     std::shared_ptr<CWallet> const wallet = GetWalletForJSONRPCRequest(request);
     CWallet *const pwallet = wallet.get();
     if (!EnsureWalletIsAvailable(pwallet, request.fHelp)) {
         return NullUniValue;
     }
 
     if (request.fHelp || request.params.size() != 2) {
         throw std::runtime_error(RPCHelpMan{
             "importprunedfunds",
             "\nImports funds without rescan. Corresponding address or script "
             "must previously be included in wallet. Aimed towards pruned "
             "wallets. The end-user is responsible to import additional "
             "transactions that subsequently spend the imported outputs or "
             "rescan after the point in the blockchain the transaction is "
             "included.\n",
             {
-                {"rawtransaction", RPCArg::Type::STR_HEX, /* opt */ false,
-                 /* default_val */ "",
+                {"rawtransaction", RPCArg::Type::STR_HEX, RPCArg::Optional::NO,
                  "A raw transaction in hex funding an already-existing "
                  "address in wallet"},
-                {"txoutproof", RPCArg::Type::STR_HEX, /* opt */ false,
-                 /* default_val */ "",
+                {"txoutproof", RPCArg::Type::STR_HEX, RPCArg::Optional::NO,
                  "The hex output from gettxoutproof that contains the "
                  "transaction"},
             },
             RPCResults{},
             RPCExamples{""},
         }
                                      .ToString());
     }
 
     CMutableTransaction tx;
     if (!DecodeHexTx(tx, request.params[0].get_str())) {
         throw JSONRPCError(RPC_DESERIALIZATION_ERROR, "TX decode failed");
     }
     uint256 txid = tx.GetId();
     CWalletTx wtx(pwallet, MakeTransactionRef(std::move(tx)));
 
     CDataStream ssMB(ParseHexV(request.params[1], "proof"), SER_NETWORK,
                      PROTOCOL_VERSION);
     CMerkleBlock merkleBlock;
     ssMB >> merkleBlock;
 
     // Search partial merkle tree in proof for our transaction and index in
     // valid block
     std::vector<uint256> vMatch;
     std::vector<size_t> vIndex;
     size_t txnIndex = 0;
     if (merkleBlock.txn.ExtractMatches(vMatch, vIndex) ==
         merkleBlock.header.hashMerkleRoot) {
         auto locked_chain = pwallet->chain().lock();
         if (locked_chain->getBlockHeight(merkleBlock.header.GetHash()) ==
             nullopt) {
             throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY,
                                "Block not found in chain");
         }
 
         std::vector<uint256>::const_iterator it;
         if ((it = std::find(vMatch.begin(), vMatch.end(), txid)) ==
             vMatch.end()) {
             throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY,
                                "Transaction given doesn't exist in proof");
         }
 
         txnIndex = vIndex[it - vMatch.begin()];
     } else {
         throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY,
                            "Something wrong with merkleblock");
     }
 
     wtx.nIndex = txnIndex;
     wtx.hashBlock = merkleBlock.header.GetHash();
 
     auto locked_chain = pwallet->chain().lock();
     LOCK(pwallet->cs_wallet);
 
     if (pwallet->IsMine(*wtx.tx)) {
         pwallet->AddToWallet(wtx, false);
         return NullUniValue;
     }
 
     throw JSONRPCError(
         RPC_INVALID_ADDRESS_OR_KEY,
         "No addresses in wallet correspond to included transaction");
 }
 
 UniValue removeprunedfunds(const Config &config,
                            const JSONRPCRequest &request) {
     std::shared_ptr<CWallet> const wallet = GetWalletForJSONRPCRequest(request);
     CWallet *const pwallet = wallet.get();
     if (!EnsureWalletIsAvailable(pwallet, request.fHelp)) {
         return NullUniValue;
     }
 
     if (request.fHelp || request.params.size() != 1) {
         throw std::runtime_error(RPCHelpMan{
             "removeprunedfunds",
             "\nDeletes the specified transaction from the wallet. Meant "
             "for use with pruned wallets and as a companion to "
             "importprunedfunds. This will affect wallet balances.\n",
             {
-                {"txid", RPCArg::Type::STR_HEX, /* opt */ false,
-                 /* default_val */ "",
+                {"txid", RPCArg::Type::STR_HEX, RPCArg::Optional::NO,
                  "The hex-encoded id of the transaction you are deleting"},
             },
             RPCResults{},
             RPCExamples{
                 HelpExampleCli("removeprunedfunds",
                                "\"a8d0c0184dde994a09ec054286f1"
                                "ce581bebf46446a512166eae762873"
                                "4ea0a5\"") +
                 "\nAs a JSON-RPC call\n" +
                 HelpExampleRpc(
                     "removeprunedfunds",
                     "\"a8d0c0184dde994a09ec054286f1ce581bebf46446a512166"
                     "eae7628734ea0a5\"")},
         }
                                      .ToString());
     }
 
     auto locked_chain = pwallet->chain().lock();
     LOCK(pwallet->cs_wallet);
 
     TxId txid(ParseHashV(request.params[0], "txid"));
     std::vector<TxId> txIds;
     txIds.push_back(txid);
     std::vector<TxId> txIdsOut;
 
     if (pwallet->ZapSelectTx(txIds, txIdsOut) != DBErrors::LOAD_OK) {
         throw JSONRPCError(RPC_WALLET_ERROR,
                            "Could not properly delete the transaction.");
     }
 
     if (txIdsOut.empty()) {
         throw JSONRPCError(RPC_INVALID_PARAMETER,
                            "Transaction does not exist in wallet.");
     }
 
     return NullUniValue;
 }
 
 UniValue importpubkey(const Config &config, const JSONRPCRequest &request) {
     std::shared_ptr<CWallet> const wallet = GetWalletForJSONRPCRequest(request);
     CWallet *const pwallet = wallet.get();
     if (!EnsureWalletIsAvailable(pwallet, request.fHelp)) {
         return NullUniValue;
     }
 
     if (request.fHelp || request.params.size() < 1 ||
         request.params.size() > 4) {
         throw std::runtime_error(RPCHelpMan{
             "importpubkey",
             "\nAdds a public key (in hex) that can be watched as if "
             "it were in your wallet but cannot be used to spend. "
             "Requires a new wallet backup.\n"
             "\nNote: This call can take minutes to complete if rescan is true, "
             "during that time, other rpc calls\n"
             "may report that the imported pubkey exists but related "
             "transactions are still missing, leading to temporarily "
             "incorrect/bogus balances and unspent outputs until rescan "
             "completes.\n",
             {
-                {"pubkey", RPCArg::Type::STR, /* opt */ false,
-                 /* default_val */ "", "The hex-encoded public key"},
-                {"label", RPCArg::Type::STR, /* opt */ true,
-                 /* default_val */ "\"\"", "An optional label"},
-                {"rescan", RPCArg::Type::BOOL, /* opt */ true,
-                 /* default_val */ "true",
+                {"pubkey", RPCArg::Type::STR, RPCArg::Optional::NO,
+                 "The hex-encoded public key"},
+                {"label", RPCArg::Type::STR, /* default */ "\"\"",
+                 "An optional label"},
+                {"rescan", RPCArg::Type::BOOL, /* default */ "true",
                  "Rescan the wallet for transactions"},
             },
             RPCResults{},
             RPCExamples{"\nImport a public key with rescan\n" +
                         HelpExampleCli("importpubkey", "\"mypubkey\"") +
                         "\nImport using a label without rescan\n" +
                         HelpExampleCli("importpubkey",
                                        "\"mypubkey\" \"testing\" false") +
                         "\nAs a JSON-RPC call\n" +
                         HelpExampleRpc("importpubkey",
                                        "\"mypubkey\", \"testing\", false")},
         }
                                      .ToString());
     }
 
     std::string strLabel;
     if (!request.params[1].isNull()) {
         strLabel = request.params[1].get_str();
     }
 
     // Whether to perform rescan after import
     bool fRescan = true;
     if (!request.params[2].isNull()) {
         fRescan = request.params[2].get_bool();
     }
 
     if (fRescan && pwallet->chain().getPruneMode()) {
         throw JSONRPCError(RPC_WALLET_ERROR,
                            "Rescan is disabled in pruned mode");
     }
 
     WalletRescanReserver reserver(pwallet);
     if (fRescan && !reserver.reserve()) {
         throw JSONRPCError(
             RPC_WALLET_ERROR,
             "Wallet is currently rescanning. Abort existing rescan or wait.");
     }
 
     if (!IsHex(request.params[0].get_str())) {
         throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY,
                            "Pubkey must be a hex string");
     }
     std::vector<uint8_t> data(ParseHex(request.params[0].get_str()));
     CPubKey pubKey(data.begin(), data.end());
     if (!pubKey.IsFullyValid()) {
         throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY,
                            "Pubkey is not a valid public key");
     }
 
     {
         auto locked_chain = pwallet->chain().lock();
         LOCK(pwallet->cs_wallet);
 
         for (const auto &dest : GetAllDestinationsForKey(pubKey)) {
             ImportAddress(pwallet, dest, strLabel);
         }
         ImportScript(pwallet, GetScriptForRawPubKey(pubKey), strLabel, false);
         pwallet->LearnAllRelatedScripts(pubKey);
     }
     if (fRescan) {
         RescanWallet(*pwallet, reserver);
         pwallet->ReacceptWalletTransactions();
     }
 
     return NullUniValue;
 }
 
 UniValue importwallet(const Config &config, const JSONRPCRequest &request) {
     std::shared_ptr<CWallet> const wallet = GetWalletForJSONRPCRequest(request);
     CWallet *const pwallet = wallet.get();
     if (!EnsureWalletIsAvailable(pwallet, request.fHelp)) {
         return NullUniValue;
     }
 
     if (request.fHelp || request.params.size() != 1) {
         throw std::runtime_error(RPCHelpMan{
             "importwallet",
             "\nImports keys from a wallet dump file (see dumpwallet). "
             "Requires a new wallet backup to include imported keys.\n",
             {
-                {"filename", RPCArg::Type::STR, /* opt */ false,
-                 /* default_val */ "", "The wallet file"},
+                {"filename", RPCArg::Type::STR, RPCArg::Optional::NO,
+                 "The wallet file"},
             },
             RPCResults{},
             RPCExamples{"\nDump the wallet\n" +
                         HelpExampleCli("dumpwallet", "\"test\"") +
                         "\nImport the wallet\n" +
                         HelpExampleCli("importwallet", "\"test\"") +
                         "\nImport using the json rpc call\n" +
                         HelpExampleRpc("importwallet", "\"test\"")},
         }
                                      .ToString());
     }
 
     if (pwallet->chain().getPruneMode()) {
         throw JSONRPCError(RPC_WALLET_ERROR,
                            "Importing wallets is disabled in pruned mode");
     }
 
     WalletRescanReserver reserver(pwallet);
     if (!reserver.reserve()) {
         throw JSONRPCError(
             RPC_WALLET_ERROR,
             "Wallet is currently rescanning. Abort existing rescan or wait.");
     }
 
     int64_t nTimeBegin = 0;
     bool fGood = true;
     {
         auto locked_chain = pwallet->chain().lock();
         LOCK(pwallet->cs_wallet);
 
         EnsureWalletIsUnlocked(pwallet);
 
         fsbridge::ifstream file;
         file.open(request.params[0].get_str(), std::ios::in | std::ios::ate);
         if (!file.is_open()) {
             throw JSONRPCError(RPC_INVALID_PARAMETER,
                                "Cannot open wallet dump file");
         }
         Optional<int> tip_height = locked_chain->getHeight();
         nTimeBegin = tip_height ? locked_chain->getBlockTime(*tip_height) : 0;
 
         int64_t nFilesize = std::max<int64_t>(1, file.tellg());
         file.seekg(0, file.beg);
 
         // Use uiInterface.ShowProgress instead of pwallet.ShowProgress because
         // pwallet.ShowProgress has a cancel button tied to AbortRescan which we
         // don't want for this progress bar showing the import progress.
         // uiInterface.ShowProgress does not have a cancel button.
 
         // show progress dialog in GUI
         pwallet->chain().showProgress(
             strprintf("%s " + _("Importing...").translated,
                       pwallet->GetDisplayName()),
             0, false);
         std::vector<std::tuple<CKey, int64_t, bool, std::string>> keys;
         std::vector<std::pair<CScript, int64_t>> scripts;
         while (file.good()) {
             pwallet->chain().showProgress(
                 "",
                 std::max(1, std::min<int>(50, 100 * double(file.tellg()) /
                                                   double(nFilesize))),
                 false);
             std::string line;
             std::getline(file, line);
             if (line.empty() || line[0] == '#') {
                 continue;
             }
 
             std::vector<std::string> vstr;
             boost::split(vstr, line, boost::is_any_of(" "));
             if (vstr.size() < 2) {
                 continue;
             }
             CKey key = DecodeSecret(vstr[0]);
             if (key.IsValid()) {
                 int64_t nTime = ParseISO8601DateTime(vstr[1]);
                 std::string strLabel;
                 bool fLabel = true;
                 for (size_t nStr = 2; nStr < vstr.size(); nStr++) {
                     if (vstr[nStr].front() == '#') {
                         break;
                     }
                     if (vstr[nStr] == "change=1") {
                         fLabel = false;
                     }
                     if (vstr[nStr] == "reserve=1") {
                         fLabel = false;
                     }
                     if (vstr[nStr].substr(0, 6) == "label=") {
                         strLabel = DecodeDumpString(vstr[nStr].substr(6));
                         fLabel = true;
                     }
                 }
                 keys.push_back(std::make_tuple(key, nTime, fLabel, strLabel));
             } else if (IsHex(vstr[0])) {
                 std::vector<uint8_t> vData(ParseHex(vstr[0]));
                 CScript script = CScript(vData.begin(), vData.end());
                 int64_t birth_time = ParseISO8601DateTime(vstr[1]);
                 scripts.push_back(
                     std::pair<CScript, int64_t>(script, birth_time));
             }
         }
         file.close();
         // We now know whether we are importing private keys, so we can error if
         // private keys are disabled
         if (keys.size() > 0 &&
             pwallet->IsWalletFlagSet(WALLET_FLAG_DISABLE_PRIVATE_KEYS)) {
             // hide progress dialog in GUI
             pwallet->chain().showProgress("", 100, false);
             throw JSONRPCError(
                 RPC_WALLET_ERROR,
                 "Importing wallets is disabled when private keys are disabled");
         }
         double total = double(keys.size() + scripts.size());
         double progress = 0;
         for (const auto &key_tuple : keys) {
             pwallet->chain().showProgress(
                 "",
                 std::max(50, std::min<int>(75, 100 * progress / total) + 50),
                 false);
             const CKey &key = std::get<0>(key_tuple);
             int64_t time = std::get<1>(key_tuple);
             bool has_label = std::get<2>(key_tuple);
             std::string label = std::get<3>(key_tuple);
 
             CPubKey pubkey = key.GetPubKey();
             assert(key.VerifyPubKey(pubkey));
             CKeyID keyid = pubkey.GetID();
             if (pwallet->HaveKey(keyid)) {
                 pwallet->WalletLogPrintf(
                     "Skipping import of %s (key already present)\n",
                     EncodeDestination(keyid, config));
                 continue;
             }
             pwallet->WalletLogPrintf("Importing %s...\n",
                                      EncodeDestination(keyid, config));
             if (!pwallet->AddKeyPubKey(key, pubkey)) {
                 fGood = false;
                 continue;
             }
             pwallet->mapKeyMetadata[keyid].nCreateTime = time;
             if (has_label) {
                 pwallet->SetAddressBook(keyid, label, "receive");
             }
             nTimeBegin = std::min(nTimeBegin, time);
             progress++;
         }
         for (const auto &script_pair : scripts) {
             pwallet->chain().showProgress(
                 "",
                 std::max(50, std::min<int>(75, 100 * progress / total) + 50),
                 false);
             const CScript &script = script_pair.first;
             int64_t time = script_pair.second;
             CScriptID id(script);
             if (pwallet->HaveCScript(id)) {
                 pwallet->WalletLogPrintf(
                     "Skipping import of %s (script already present)\n",
                     HexStr(script));
                 continue;
             }
             if (!pwallet->AddCScript(script)) {
                 pwallet->WalletLogPrintf("Error importing script %s\n",
                                          HexStr(script));
                 fGood = false;
                 continue;
             }
             if (time > 0) {
                 pwallet->m_script_metadata[id].nCreateTime = time;
                 nTimeBegin = std::min(nTimeBegin, time);
             }
             progress++;
         }
         // hide progress dialog in GUI
         pwallet->chain().showProgress("", 100, false);
         pwallet->UpdateTimeFirstKey(nTimeBegin);
     }
     // hide progress dialog in GUI
     pwallet->chain().showProgress("", 100, false);
     RescanWallet(*pwallet, reserver, nTimeBegin, false /* update */);
     pwallet->MarkDirty();
 
     if (!fGood) {
         throw JSONRPCError(RPC_WALLET_ERROR,
                            "Error adding some keys/scripts to wallet");
     }
 
     return NullUniValue;
 }
 
 UniValue dumpprivkey(const Config &config, const JSONRPCRequest &request) {
     std::shared_ptr<CWallet> const wallet = GetWalletForJSONRPCRequest(request);
     CWallet *const pwallet = wallet.get();
     if (!EnsureWalletIsAvailable(pwallet, request.fHelp)) {
         return NullUniValue;
     }
 
     if (request.fHelp || request.params.size() != 1) {
         throw std::runtime_error(RPCHelpMan{
             "dumpprivkey",
             "\nReveals the private key corresponding to 'address'.\n"
             "Then the importprivkey can be used with this output\n",
             {
-                {"address", RPCArg::Type::STR, /* opt */ false,
-                 /* default_val */ "",
+                {"address", RPCArg::Type::STR, RPCArg::Optional::NO,
                  "The bitcoin address for the private key"},
             },
             RPCResult{"\"key\"                (string) The private key\n"},
             RPCExamples{HelpExampleCli("dumpprivkey", "\"myaddress\"") +
                         HelpExampleCli("importprivkey", "\"mykey\"") +
                         HelpExampleRpc("dumpprivkey", "\"myaddress\"")},
         }
                                      .ToString());
     }
 
     auto locked_chain = pwallet->chain().lock();
     LOCK(pwallet->cs_wallet);
 
     EnsureWalletIsUnlocked(pwallet);
 
     std::string strAddress = request.params[0].get_str();
     CTxDestination dest =
         DecodeDestination(strAddress, config.GetChainParams());
     if (!IsValidDestination(dest)) {
         throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY,
                            "Invalid Bitcoin address");
     }
     auto keyid = GetKeyForDestination(*pwallet, dest);
     if (keyid.IsNull()) {
         throw JSONRPCError(RPC_TYPE_ERROR, "Address does not refer to a key");
     }
     CKey vchSecret;
     if (!pwallet->GetKey(keyid, vchSecret)) {
         throw JSONRPCError(RPC_WALLET_ERROR, "Private key for address " +
                                                  strAddress + " is not known");
     }
     return EncodeSecret(vchSecret);
 }
 
 UniValue dumpwallet(const Config &config, const JSONRPCRequest &request) {
     std::shared_ptr<CWallet> const wallet = GetWalletForJSONRPCRequest(request);
     CWallet *const pwallet = wallet.get();
     if (!EnsureWalletIsAvailable(pwallet, request.fHelp)) {
         return NullUniValue;
     }
 
     if (request.fHelp || request.params.size() != 1) {
         throw std::runtime_error(RPCHelpMan{
             "dumpwallet",
             "\nDumps all wallet keys in a human-readable format to "
             "a server-side file. This does not allow overwriting "
             "existing files.\n"
             "Imported scripts are included in the dumpsfile, but "
             "corresponding addresses may not be added automatically "
             "by importwallet.\n"
             "Note that if your wallet contains keys which are not "
             "derived from your HD seed (e.g. imported keys), these "
             "are not covered by\n"
             "only backing up the seed itself, and must be backed up "
             "too (e.g. ensure you back up the whole dumpfile).\n",
             {
-                {"filename", RPCArg::Type::STR, /* opt */ false,
-                 /* default_val */ "",
+                {"filename", RPCArg::Type::STR, RPCArg::Optional::NO,
                  "The filename with path (either absolute or relative to "
                  "bitcoind)"},
             },
             RPCResult{
                 "{                           (json object)\n"
                 "  \"filename\" : {        (string) The filename with full "
                 "absolute path\n"
                 "}\n"},
             RPCExamples{HelpExampleCli("dumpwallet", "\"test\"") +
                         HelpExampleRpc("dumpwallet", "\"test\"")},
         }
                                      .ToString());
     }
 
     auto locked_chain = pwallet->chain().lock();
     LOCK(pwallet->cs_wallet);
 
     EnsureWalletIsUnlocked(pwallet);
 
     fs::path filepath = request.params[0].get_str();
     filepath = fs::absolute(filepath);
 
     /**
      * Prevent arbitrary files from being overwritten. There have been reports
      * that users have overwritten wallet files this way:
      * https://github.com/bitcoin/bitcoin/issues/9934
      * It may also avoid other security issues.
      */
     if (fs::exists(filepath)) {
         throw JSONRPCError(RPC_INVALID_PARAMETER,
                            filepath.string() + " already exists. If you are "
                                                "sure this is what you want, "
                                                "move it out of the way first");
     }
 
     fsbridge::ofstream file;
     file.open(filepath);
     if (!file.is_open()) {
         throw JSONRPCError(RPC_INVALID_PARAMETER,
                            "Cannot open wallet dump file");
     }
 
     std::map<CTxDestination, int64_t> mapKeyBirth;
     const std::map<CKeyID, int64_t> &mapKeyPool = pwallet->GetAllReserveKeys();
     pwallet->GetKeyBirthTimes(*locked_chain, mapKeyBirth);
 
     std::set<CScriptID> scripts = pwallet->GetCScripts();
     // TODO: include scripts in GetKeyBirthTimes() output instead of separate
 
     // sort time/key pairs
     std::vector<std::pair<int64_t, CKeyID>> vKeyBirth;
     for (const auto &entry : mapKeyBirth) {
         if (const CKeyID *keyID = boost::get<CKeyID>(&entry.first)) {
             // set and test
             vKeyBirth.push_back(std::make_pair(entry.second, *keyID));
         }
     }
     mapKeyBirth.clear();
     std::sort(vKeyBirth.begin(), vKeyBirth.end());
 
     // produce output
     file << strprintf("# Wallet dump created by Bitcoin %s\n", CLIENT_BUILD);
     file << strprintf("# * Created on %s\n", FormatISO8601DateTime(GetTime()));
     const Optional<int> tip_height = locked_chain->getHeight();
     file << strprintf("# * Best block at time of backup was %i (%s),\n",
                       tip_height.value_or(-1),
                       tip_height
                           ? locked_chain->getBlockHash(*tip_height).ToString()
                           : "(missing block hash)");
     file << strprintf("#   mined on %s\n",
                       tip_height ? FormatISO8601DateTime(
                                        locked_chain->getBlockTime(*tip_height))
                                  : "(missing block time)");
     file << "\n";
 
     // add the base58check encoded extended master if the wallet uses HD
     CKeyID seed_id = pwallet->GetHDChain().seed_id;
     if (!seed_id.IsNull()) {
         CKey seed;
         if (pwallet->GetKey(seed_id, seed)) {
             CExtKey masterKey;
             masterKey.SetSeed(seed.begin(), seed.size());
 
             file << "# extended private masterkey: " << EncodeExtKey(masterKey)
                  << "\n\n";
         }
     }
     for (std::vector<std::pair<int64_t, CKeyID>>::const_iterator it =
              vKeyBirth.begin();
          it != vKeyBirth.end(); it++) {
         const CKeyID &keyid = it->second;
         std::string strTime = FormatISO8601DateTime(it->first);
         std::string strAddr;
         std::string strLabel;
         CKey key;
         if (pwallet->GetKey(keyid, key)) {
             file << strprintf("%s %s ", EncodeSecret(key), strTime);
             if (GetWalletAddressesForKey(config, pwallet, keyid, strAddr,
                                          strLabel)) {
                 file << strprintf("label=%s", strLabel);
             } else if (keyid == seed_id) {
                 file << "hdseed=1";
             } else if (mapKeyPool.count(keyid)) {
                 file << "reserve=1";
             } else if (pwallet->mapKeyMetadata[keyid].hdKeypath == "s") {
                 file << "inactivehdseed=1";
             } else {
                 file << "change=1";
             }
             file << strprintf(
                 " # addr=%s%s\n", strAddr,
                 (pwallet->mapKeyMetadata[keyid].hdKeypath.size() > 0
                      ? " hdkeypath=" + pwallet->mapKeyMetadata[keyid].hdKeypath
                      : ""));
         }
     }
     file << "\n";
     for (const CScriptID &scriptid : scripts) {
         CScript script;
         std::string create_time = "0";
         std::string address = EncodeDestination(scriptid, config);
         // get birth times for scripts with metadata
         auto it = pwallet->m_script_metadata.find(scriptid);
         if (it != pwallet->m_script_metadata.end()) {
             create_time = FormatISO8601DateTime(it->second.nCreateTime);
         }
         if (pwallet->GetCScript(scriptid, script)) {
             file << strprintf("%s %s script=1",
                               HexStr(script.begin(), script.end()),
                               create_time);
             file << strprintf(" # addr=%s\n", address);
         }
     }
     file << "\n";
     file << "# End of dump\n";
     file.close();
 
     UniValue reply(UniValue::VOBJ);
     reply.pushKV("filename", filepath.string());
 
     return reply;
 }
 
 struct ImportData {
     // Input data
     //! Provided redeemScript; will be moved to `import_scripts` if relevant.
     std::unique_ptr<CScript> redeemscript;
 
     // Output data
     std::set<CScript> import_scripts;
     //! Import these private keys if available (the value indicates whether if
     //! the key is required for solvability)
     std::map<CKeyID, bool> used_keys;
 };
 
 enum class ScriptContext {
     //! Top-level scriptPubKey
     TOP,
     //! P2SH redeemScript
     P2SH,
 };
 
 // Analyse the provided scriptPubKey, determining which keys and which redeem
 // scripts from the ImportData struct are needed to spend it, and mark them as
 // used. Returns an error string, or the empty string for success.
 static std::string RecurseImportData(const CScript &script,
                                      ImportData &import_data,
                                      const ScriptContext script_ctx) {
     // Use Solver to obtain script type and parsed pubkeys or hashes:
     std::vector<std::vector<uint8_t>> solverdata;
     txnouttype script_type = Solver(script, solverdata);
 
     switch (script_type) {
         case TX_PUBKEY: {
             CPubKey pubkey(solverdata[0].begin(), solverdata[0].end());
             import_data.used_keys.emplace(pubkey.GetID(), false);
             return "";
         }
         case TX_PUBKEYHASH: {
             CKeyID id = CKeyID(uint160(solverdata[0]));
             import_data.used_keys[id] = true;
             return "";
         }
         case TX_SCRIPTHASH: {
             if (script_ctx == ScriptContext::P2SH) {
                 throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY,
                                    "Trying to nest P2SH inside another P2SH");
             }
             assert(script_ctx == ScriptContext::TOP);
             CScriptID id = CScriptID(uint160(solverdata[0]));
             // Remove redeemscript from import_data to check for superfluous
             // script later.
             auto subscript = std::move(import_data.redeemscript);
             if (!subscript) {
                 return "missing redeemscript";
             }
             if (CScriptID(*subscript) != id) {
                 return "redeemScript does not match the scriptPubKey";
             }
             import_data.import_scripts.emplace(*subscript);
             return RecurseImportData(*subscript, import_data,
                                      ScriptContext::P2SH);
         }
         case TX_MULTISIG: {
             for (size_t i = 1; i + 1 < solverdata.size(); ++i) {
                 CPubKey pubkey(solverdata[i].begin(), solverdata[i].end());
                 import_data.used_keys.emplace(pubkey.GetID(), false);
             }
             return "";
         }
         case TX_NULL_DATA:
             return "unspendable script";
         case TX_NONSTANDARD:
         default:
             return "unrecognized script";
     }
 }
 
 static UniValue ProcessImportLegacy(CWallet *const pwallet,
                                     ImportData &import_data,
                                     std::map<CKeyID, CPubKey> &pubkey_map,
                                     std::map<CKeyID, CKey> &privkey_map,
                                     std::set<CScript> &script_pub_keys,
                                     bool &have_solving_data,
                                     const UniValue &data) {
     UniValue warnings(UniValue::VARR);
 
     // First ensure scriptPubKey has either a script or JSON with "address"
     // string
     const UniValue &scriptPubKey = data["scriptPubKey"];
     bool isScript = scriptPubKey.getType() == UniValue::VSTR;
     if (!isScript && !(scriptPubKey.getType() == UniValue::VOBJ &&
                        scriptPubKey.exists("address"))) {
         throw JSONRPCError(RPC_INVALID_PARAMETER,
                            "scriptPubKey must be string with script or JSON "
                            "with address string");
     }
     const std::string &output =
         isScript ? scriptPubKey.get_str() : scriptPubKey["address"].get_str();
 
     // Optional fields.
     const std::string &strRedeemScript =
         data.exists("redeemscript") ? data["redeemscript"].get_str() : "";
     const UniValue &pubKeys =
         data.exists("pubkeys") ? data["pubkeys"].get_array() : UniValue();
     const UniValue &keys =
         data.exists("keys") ? data["keys"].get_array() : UniValue();
     const bool internal =
         data.exists("internal") ? data["internal"].get_bool() : false;
     const bool watchOnly =
         data.exists("watchonly") ? data["watchonly"].get_bool() : false;
 
     if (data.exists("range")) {
         throw JSONRPCError(
             RPC_INVALID_PARAMETER,
             "Range should not be specified for a non-descriptor import");
     }
 
     // Generate the script and destination for the scriptPubKey provided
     CScript script;
     if (!isScript) {
         CTxDestination dest = DecodeDestination(output, pwallet->chainParams);
         if (!IsValidDestination(dest)) {
             throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY,
                                "Invalid address \"" + output + "\"");
         }
         script = GetScriptForDestination(dest);
     } else {
         if (!IsHex(output)) {
             throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY,
                                "Invalid scriptPubKey \"" + output + "\"");
         }
         std::vector<uint8_t> vData(ParseHex(output));
         script = CScript(vData.begin(), vData.end());
         CTxDestination dest;
         if (!ExtractDestination(script, dest) && !internal) {
             throw JSONRPCError(RPC_INVALID_PARAMETER,
                                "Internal must be set to true for "
                                "nonstandard scriptPubKey imports.");
         }
     }
     script_pub_keys.emplace(script);
 
     // Parse all arguments
     if (strRedeemScript.size()) {
         if (!IsHex(strRedeemScript)) {
             throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY,
                                "Invalid redeem script \"" + strRedeemScript +
                                    "\": must be hex string");
         }
         auto parsed_redeemscript = ParseHex(strRedeemScript);
         import_data.redeemscript = std::make_unique<CScript>(
             parsed_redeemscript.begin(), parsed_redeemscript.end());
     }
     for (size_t i = 0; i < pubKeys.size(); ++i) {
         const auto &str = pubKeys[i].get_str();
         if (!IsHex(str)) {
             throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY,
                                "Pubkey \"" + str + "\" must be a hex string");
         }
         auto parsed_pubkey = ParseHex(str);
         CPubKey pubkey(parsed_pubkey.begin(), parsed_pubkey.end());
         if (!pubkey.IsFullyValid()) {
             throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY,
                                "Pubkey \"" + str +
                                    "\" is not a valid public key");
         }
         pubkey_map.emplace(pubkey.GetID(), pubkey);
     }
     for (size_t i = 0; i < keys.size(); ++i) {
         const auto &str = keys[i].get_str();
         CKey key = DecodeSecret(str);
         if (!key.IsValid()) {
             throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY,
                                "Invalid private key encoding");
         }
         CPubKey pubkey = key.GetPubKey();
         CKeyID id = pubkey.GetID();
         if (pubkey_map.count(id)) {
             pubkey_map.erase(id);
         }
         privkey_map.emplace(id, key);
     }
 
     // Verify and process input data
     have_solving_data =
         import_data.redeemscript || pubkey_map.size() || privkey_map.size();
     if (have_solving_data) {
         // Match up data in import_data with the scriptPubKey in script.
         auto error = RecurseImportData(script, import_data, ScriptContext::TOP);
 
         // Verify whether the watchonly option corresponds to the
         // availability of private keys.
         bool spendable = std::all_of(
             import_data.used_keys.begin(), import_data.used_keys.end(),
             [&](const std::pair<CKeyID, bool> &used_key) {
                 return privkey_map.count(used_key.first) > 0;
             });
         if (!watchOnly && !spendable) {
             warnings.push_back("Some private keys are missing, outputs "
                                "will be considered watchonly. If this is "
                                "intentional, specify the watchonly flag.");
         }
         if (watchOnly && spendable) {
             warnings.push_back(
                 "All private keys are provided, outputs will be considered "
                 "spendable. If this is intentional, do not specify the "
                 "watchonly flag.");
         }
 
         // Check that all required keys for solvability are provided.
         if (error.empty()) {
             for (const auto &require_key : import_data.used_keys) {
                 if (!require_key.second) {
                     // Not a required key
                     continue;
                 }
 
                 if (pubkey_map.count(require_key.first) == 0 &&
                     privkey_map.count(require_key.first) == 0) {
                     error = "some required keys are missing";
                 }
             }
         }
 
         if (!error.empty()) {
             warnings.push_back("Importing as non-solvable: " + error +
                                ". If this is intentional, don't provide "
                                "any keys, pubkeys or redeemscript.");
             import_data = ImportData();
             pubkey_map.clear();
             privkey_map.clear();
             have_solving_data = false;
         } else {
             // RecurseImportData() removes any relevant redeemscript from
             // import_data, so we can use that to discover if a superfluous
             // one was provided.
             if (import_data.redeemscript) {
                 warnings.push_back(
                     "Ignoring redeemscript as this is not a P2SH script.");
             }
             for (auto it = privkey_map.begin(); it != privkey_map.end();) {
                 auto oldit = it++;
                 if (import_data.used_keys.count(oldit->first) == 0) {
                     warnings.push_back("Ignoring irrelevant private key.");
                     privkey_map.erase(oldit);
                 }
             }
             for (auto it = pubkey_map.begin(); it != pubkey_map.end();) {
                 auto oldit = it++;
                 auto key_data_it = import_data.used_keys.find(oldit->first);
                 if (key_data_it == import_data.used_keys.end() ||
                     !key_data_it->second) {
                     warnings.push_back("Ignoring public key \"" +
                                        HexStr(oldit->first) +
                                        "\" as it doesn't appear inside P2PKH.");
                     pubkey_map.erase(oldit);
                 }
             }
         }
     }
 
     return warnings;
 }
 
 static UniValue ProcessImportDescriptor(ImportData &import_data,
                                         std::map<CKeyID, CPubKey> &pubkey_map,
                                         std::map<CKeyID, CKey> &privkey_map,
                                         std::set<CScript> &script_pub_keys,
                                         bool &have_solving_data,
                                         const UniValue &data) {
     UniValue warnings(UniValue::VARR);
 
     const std::string &descriptor = data["desc"].get_str();
     FlatSigningProvider keys;
     auto parsed_desc = Parse(descriptor, keys);
     if (!parsed_desc) {
         throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Descriptor is invalid");
     }
 
     have_solving_data = parsed_desc->IsSolvable();
     const bool watch_only =
         data.exists("watchonly") ? data["watchonly"].get_bool() : false;
 
     int64_t range_start = 0, range_end = 0;
     if (!parsed_desc->IsRange() && data.exists("range")) {
         throw JSONRPCError(
             RPC_INVALID_PARAMETER,
             "Range should not be specified for an un-ranged descriptor");
     } else if (parsed_desc->IsRange()) {
         if (!data.exists("range")) {
             throw JSONRPCError(
                 RPC_INVALID_PARAMETER,
                 "Descriptor is ranged, please specify the range");
         }
         const UniValue &range = data["range"];
         range_start = range.exists("start") ? range["start"].get_int64() : 0;
         if (!range.exists("end")) {
             throw JSONRPCError(RPC_INVALID_PARAMETER,
                                "End of range for descriptor must be specified");
         }
         range_end = range["end"].get_int64();
         if (range_end < range_start || range_start < 0) {
             throw JSONRPCError(RPC_INVALID_PARAMETER,
                                "Invalid descriptor range specified");
         }
     }
 
     const UniValue &priv_keys =
         data.exists("keys") ? data["keys"].get_array() : UniValue();
 
     FlatSigningProvider out_keys;
 
     // Expand all descriptors to get public keys and scripts.
     // TODO: get private keys from descriptors too
     for (int i = range_start; i <= range_end; ++i) {
         std::vector<CScript> scripts_temp;
         parsed_desc->Expand(i, keys, scripts_temp, out_keys);
         std::copy(scripts_temp.begin(), scripts_temp.end(),
                   std::inserter(script_pub_keys, script_pub_keys.end()));
     }
 
     for (const auto &x : out_keys.scripts) {
         import_data.import_scripts.emplace(x.second);
     }
 
     std::copy(out_keys.pubkeys.begin(), out_keys.pubkeys.end(),
               std::inserter(pubkey_map, pubkey_map.end()));
 
     for (size_t i = 0; i < priv_keys.size(); ++i) {
         const auto &str = priv_keys[i].get_str();
         CKey key = DecodeSecret(str);
         if (!key.IsValid()) {
             throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY,
                                "Invalid private key encoding");
         }
         CPubKey pubkey = key.GetPubKey();
         CKeyID id = pubkey.GetID();
 
         // Check if this private key corresponds to a public key from the
         // descriptor
         if (!pubkey_map.count(id)) {
             warnings.push_back("Ignoring irrelevant private key.");
         } else {
             privkey_map.emplace(id, key);
         }
     }
 
     // Check if all the public keys have corresponding private keys in the
     // import for spendability. This does not take into account threshold
     // multisigs which could be spendable without all keys. Thus, threshold
     // multisigs without all keys will be considered not spendable here, even if
     // they are, perhaps triggering a false warning message. This is consistent
     // with the current wallet IsMine check.
     bool spendable =
         std::all_of(pubkey_map.begin(), pubkey_map.end(),
                     [&](const std::pair<CKeyID, CPubKey> &used_key) {
                         return privkey_map.count(used_key.first) > 0;
                     });
     if (!watch_only && !spendable) {
         warnings.push_back(
             "Some private keys are missing, outputs will be considered "
             "watchonly. If this is intentional, specify the watchonly flag.");
     }
     if (watch_only && spendable) {
         warnings.push_back("All private keys are provided, outputs will be "
                            "considered spendable. If this is intentional, do "
                            "not specify the watchonly flag.");
     }
 
     return warnings;
 }
 
 static UniValue ProcessImport(CWallet *const pwallet, const UniValue &data,
                               const int64_t timestamp)
     EXCLUSIVE_LOCKS_REQUIRED(pwallet->cs_wallet) {
     UniValue warnings(UniValue::VARR);
     UniValue result(UniValue::VOBJ);
 
     try {
         const bool internal =
             data.exists("internal") ? data["internal"].get_bool() : false;
         // Internal addresses should not have a label
         if (internal && data.exists("label")) {
             throw JSONRPCError(RPC_INVALID_PARAMETER,
                                "Internal addresses should not have a label");
         }
         const std::string &label =
             data.exists("label") ? data["label"].get_str() : "";
 
         ImportData import_data;
         std::map<CKeyID, CPubKey> pubkey_map;
         std::map<CKeyID, CKey> privkey_map;
         std::set<CScript> script_pub_keys;
         bool have_solving_data;
 
         if (data.exists("scriptPubKey") && data.exists("desc")) {
             throw JSONRPCError(
                 RPC_INVALID_PARAMETER,
                 "Both a descriptor and a scriptPubKey should not be provided.");
         } else if (data.exists("scriptPubKey")) {
             warnings = ProcessImportLegacy(pwallet, import_data, pubkey_map,
                                            privkey_map, script_pub_keys,
                                            have_solving_data, data);
         } else if (data.exists("desc")) {
             warnings = ProcessImportDescriptor(import_data, pubkey_map,
                                                privkey_map, script_pub_keys,
                                                have_solving_data, data);
         } else {
             throw JSONRPCError(
                 RPC_INVALID_PARAMETER,
                 "Either a descriptor or scriptPubKey must be provided.");
         }
 
         // If private keys are disabled, abort if private keys are being
         // imported
         if (pwallet->IsWalletFlagSet(WALLET_FLAG_DISABLE_PRIVATE_KEYS) &&
             !privkey_map.empty()) {
             throw JSONRPCError(RPC_WALLET_ERROR,
                                "Cannot import private keys to a wallet with "
                                "private keys disabled");
         }
 
         // Check whether we have any work to do
         for (const CScript &script : script_pub_keys) {
             if (::IsMine(*pwallet, script) & ISMINE_SPENDABLE) {
                 throw JSONRPCError(RPC_WALLET_ERROR,
                                    "The wallet already contains the private "
                                    "key for this address or script (\"" +
                                        HexStr(script.begin(), script.end()) +
                                        "\")");
             }
         }
 
         // All good, time to import
         pwallet->MarkDirty();
 
         for (const auto &entry : import_data.import_scripts) {
             if (!pwallet->HaveCScript(CScriptID(entry)) &&
                 !pwallet->AddCScript(entry)) {
                 throw JSONRPCError(RPC_WALLET_ERROR,
                                    "Error adding script to wallet");
             }
         }
         for (const auto &entry : privkey_map) {
             const CKey &key = entry.second;
             CPubKey pubkey = key.GetPubKey();
             const CKeyID &id = entry.first;
             assert(key.VerifyPubKey(pubkey));
             pwallet->mapKeyMetadata[id].nCreateTime = timestamp;
             // If the private key is not present in the wallet, insert it.
             if (!pwallet->HaveKey(id) && !pwallet->AddKeyPubKey(key, pubkey)) {
                 throw JSONRPCError(RPC_WALLET_ERROR,
                                    "Error adding key to wallet");
             }
             pwallet->UpdateTimeFirstKey(timestamp);
         }
         for (const auto &entry : pubkey_map) {
             const CPubKey &pubkey = entry.second;
             const CKeyID &id = entry.first;
             CPubKey temp;
             if (!pwallet->GetPubKey(id, temp) &&
                 !pwallet->AddWatchOnly(GetScriptForRawPubKey(pubkey),
                                        timestamp)) {
                 throw JSONRPCError(RPC_WALLET_ERROR,
                                    "Error adding address to wallet");
             }
         }
 
         for (const CScript &script : script_pub_keys) {
             if (!have_solving_data || !::IsMine(*pwallet, script)) {
                 // Always call AddWatchOnly for non-solvable watch-only, so that
                 // watch timestamp gets updated
                 if (!pwallet->AddWatchOnly(script, timestamp)) {
                     throw JSONRPCError(RPC_WALLET_ERROR,
                                        "Error adding address to wallet");
                 }
             }
             CTxDestination dest;
             ExtractDestination(script, dest);
             if (!internal && IsValidDestination(dest)) {
                 pwallet->SetAddressBook(dest, label, "receive");
             }
         }
 
         result.pushKV("success", UniValue(true));
     } catch (const UniValue &e) {
         result.pushKV("success", UniValue(false));
         result.pushKV("error", e);
     } catch (...) {
         result.pushKV("success", UniValue(false));
         result.pushKV("error",
                       JSONRPCError(RPC_MISC_ERROR, "Missing required fields"));
     }
 
     if (warnings.size()) {
         result.pushKV("warnings", warnings);
     }
     return result;
 }
 
 static int64_t GetImportTimestamp(const UniValue &data, int64_t now) {
     if (data.exists("timestamp")) {
         const UniValue &timestamp = data["timestamp"];
         if (timestamp.isNum()) {
             return timestamp.get_int64();
         } else if (timestamp.isStr() && timestamp.get_str() == "now") {
             return now;
         }
         throw JSONRPCError(RPC_TYPE_ERROR,
                            strprintf("Expected number or \"now\" timestamp "
                                      "value for key. got type %s",
                                      uvTypeName(timestamp.type())));
     }
     throw JSONRPCError(RPC_TYPE_ERROR,
                        "Missing required timestamp field for key");
 }
 
 UniValue importmulti(const Config &config, const JSONRPCRequest &mainRequest) {
     std::shared_ptr<CWallet> const wallet =
         GetWalletForJSONRPCRequest(mainRequest);
     CWallet *const pwallet = wallet.get();
     if (!EnsureWalletIsAvailable(pwallet, mainRequest.fHelp)) {
         return NullUniValue;
     }
 
     if (mainRequest.fHelp || mainRequest.params.size() < 1 ||
         mainRequest.params.size() > 2) {
         throw std::runtime_error(RPCHelpMan{
             "importmulti",
             "\nImport addresses/scripts (with private or public keys, redeem "
             "script (P2SH)), rescanning all addresses in one-shot-only (rescan "
             "can be disabled via options). Requires a new wallet backup.\n",
             {
                 {"requests",
                  RPCArg::Type::ARR,
-                 /* opt */ false,
-                 /* default_val */ "",
+                 RPCArg::Optional::NO,
                  "Data to be imported",
                  {
                      {
                          "",
                          RPCArg::Type::OBJ,
-                         /* opt */ false,
-                         /* default_val */ "",
+                         RPCArg::Optional::OMITTED,
                          "",
                          {
-                             {"desc", RPCArg::Type::STR, /* opt */ true,
-                              /* default_val */ "",
+                             {"desc", RPCArg::Type::STR,
+                              RPCArg::Optional::OMITTED,
                               "Descriptor to import. If using descriptor, do "
                               "not also provide address/scriptPubKey, scripts, "
                               "or pubkeys"},
                              {"scriptPubKey",
                               RPCArg::Type::STR,
-                              /* opt */ false,
-                              /* default_val */ "",
+                              RPCArg::Optional::NO,
                               "Type of scriptPubKey (string for script, json "
                               "for address). Should not be provided if using a "
                               "descriptor",
                               /* oneline_description */ "",
                               {"\"<script>\" | { \"address\":\"<address>\" }",
                                "string / json"}},
                              {"timestamp",
                               RPCArg::Type::NUM,
-                              /* opt */ false,
-                              /* default_val */ "",
+                              RPCArg::Optional::NO,
                               "Creation time of the key in seconds since "
                               "epoch (Jan 1 1970 GMT),\n"
                               "                                            "
                               "                  or the string \"now\" to "
                               "substitute the current synced blockchain "
                               "time. The timestamp of the oldest\n"
                               "                                            "
                               "                  key will determine how "
                               "far back blockchain rescans need to begin "
                               "for missing wallet transactions.\n"
                               "                                            "
                               "                  \"now\" can be specified "
                               "to bypass scanning, for keys which are "
                               "known to never have been used, and\n"
                               "                                            "
                               "                  0 can be specified to "
                               "scan the entire blockchain. Blocks up to 2 "
                               "hours before the earliest key\n"
                               "                                            "
                               "                  creation time of all keys "
                               "being imported by the importmulti call will "
                               "be scanned.",
                               /* oneline_description */ "",
                               {"timestamp | \"now\"", "integer / string"}},
-                             {"redeemscript", RPCArg::Type::STR, /* opt */ true,
-                              /* default_val */ "omitted",
+                             {"redeemscript", RPCArg::Type::STR,
+                              RPCArg::Optional::OMITTED,
                               "Allowed only if the scriptPubKey is a P2SH "
                               "address/scriptPubKey"},
                              {"pubkeys",
                               RPCArg::Type::ARR,
-                              /* opt */ true,
-                              /* default_val */ "empty array",
+                              /* default */ "empty array",
                               "Array of strings giving pubkeys to import. They "
                               "must occur in P2PKH scripts. They are not "
                               "required when the private key is also provided "
                               "(see the \"keys\" argument).",
                               {
-                                  {"pubKey", RPCArg::Type::STR, /* opt */ false,
-                                   /* default_val */ "", ""},
+                                  {"pubKey", RPCArg::Type::STR,
+                                   RPCArg::Optional::OMITTED, ""},
                               }},
                              {"keys",
                               RPCArg::Type::ARR,
-                              /* opt */ true,
-                              /* default_val */ "empty array",
+                              /* default */ "empty array",
                               "Array of strings giving private keys to import. "
                               "The corresponding public keys must occur in the "
                               "output or redeemscript.",
                               {
                                   {"key", RPCArg::Type::STR,
-                                   /* opt */ false, /* default_val */ "", ""},
+                                   RPCArg::Optional::OMITTED, ""},
                               }},
                              {"range",
                               RPCArg::Type::OBJ,
-                              /* opt */ true,
-                              /* default_val */ "",
+                              RPCArg::Optional::OMITTED,
                               "If a ranged descriptor is used, this specifies "
                               "the start and end of the range to import",
                               {
-                                  {"start", RPCArg::Type::NUM, /* opt */ true,
-                                   /* default_val */ "0",
+                                  {"start", RPCArg::Type::NUM,
+                                   /* default */ "0",
                                    "Start of the range to import"},
-                                  {"end", RPCArg::Type::NUM, /* opt */ false,
-                                   /* default_val */ "",
+                                  {"end", RPCArg::Type::NUM,
+                                   RPCArg::Optional::NO,
                                    "End of the range to import (inclusive)"},
                               }},
                              {"internal", RPCArg::Type::BOOL,
-                              /* opt */ true, /* default_val */ "false",
+                              /* default */ "false",
                               "Stating whether matching outputs should be "
                               "treated as not incoming payments (also known as "
                               "change)"},
                              {"watchonly", RPCArg::Type::BOOL,
-                              /* opt */ true, /* default_val */ "false",
+                              /* default */ "false",
                               "Stating whether matching outputs should be "
                               "considered watched even when not all private "
                               "keys are provided."},
-                             {"label", RPCArg::Type::STR, /* opt */ true,
-                              /* default_val */ "''",
+                             {"label", RPCArg::Type::STR, /* default */ "''",
                               "Label to assign to the address, only "
                               "allowed with internal=false"},
                          },
                      },
                  },
                  "\"requests\""},
                 {"options",
                  RPCArg::Type::OBJ,
-                 /* opt */ true,
-                 /* default_val */ "null",
+                 RPCArg::Optional::OMITTED_NAMED_ARG,
                  "",
                  {
-                     {"rescan", RPCArg::Type::BOOL, /* opt */ true,
-                      /* default_val */ "true",
+                     {"rescan", RPCArg::Type::BOOL, /* default */ "true",
                       "Stating if should rescan the blockchain after all "
                       "imports"},
                  },
                  "\"options\""},
             },
             RPCResult{"\nResponse is an array with the same size as the input "
                       "that has the execution result :\n"
                       "  [{\"success\": true}, {\"success\": true, "
                       "\"warnings\": [\"Ignoring irrelevant private key\"]}, "
                       "{\"success\": false, \"error\": {\"code\": -1, "
                       "\"message\": \"Internal Server Error\"}}, ...]\n"},
             RPCExamples{
                 HelpExampleCli(
                     "importmulti",
                     "'[{ \"scriptPubKey\": { \"address\": \"<my address>\" }, "
                     "\"timestamp\":1455191478 }, "
                     "{ \"scriptPubKey\": { \"address\": \"<my 2nd address>\" "
                     "}, "
                     "\"label\": \"example 2\", \"timestamp\": 1455191480 }]'") +
                 HelpExampleCli(
                     "importmulti",
                     "'[{ \"scriptPubKey\": { \"address\": \"<my address>\" }, "
                     "\"timestamp\":1455191478 }]' '{ \"rescan\": false}'")
 
             },
         }
                                      .ToString());
     }
 
     RPCTypeCheck(mainRequest.params, {UniValue::VARR, UniValue::VOBJ});
 
     const UniValue &requests = mainRequest.params[0];
 
     // Default options
     bool fRescan = true;
 
     if (!mainRequest.params[1].isNull()) {
         const UniValue &options = mainRequest.params[1];
 
         if (options.exists("rescan")) {
             fRescan = options["rescan"].get_bool();
         }
     }
 
     WalletRescanReserver reserver(pwallet);
     if (fRescan && !reserver.reserve()) {
         throw JSONRPCError(
             RPC_WALLET_ERROR,
             "Wallet is currently rescanning. Abort existing rescan or wait.");
     }
 
     int64_t now = 0;
     bool fRunScan = false;
     int64_t nLowestTimestamp = 0;
     UniValue response(UniValue::VARR);
     {
         auto locked_chain = pwallet->chain().lock();
         LOCK(pwallet->cs_wallet);
         EnsureWalletIsUnlocked(pwallet);
 
         // Verify all timestamps are present before importing any keys.
         const Optional<int> tip_height = locked_chain->getHeight();
         now =
             tip_height ? locked_chain->getBlockMedianTimePast(*tip_height) : 0;
         for (const UniValue &data : requests.getValues()) {
             GetImportTimestamp(data, now);
         }
 
         const int64_t minimumTimestamp = 1;
 
         if (fRescan && tip_height) {
             nLowestTimestamp = locked_chain->getBlockTime(*tip_height);
         } else {
             fRescan = false;
         }
 
         for (const UniValue &data : requests.getValues()) {
             const int64_t timestamp =
                 std::max(GetImportTimestamp(data, now), minimumTimestamp);
             const UniValue result = ProcessImport(pwallet, data, timestamp);
             response.push_back(result);
 
             if (!fRescan) {
                 continue;
             }
 
             // If at least one request was successful then allow rescan.
             if (result["success"].get_bool()) {
                 fRunScan = true;
             }
 
             // Get the lowest timestamp.
             if (timestamp < nLowestTimestamp) {
                 nLowestTimestamp = timestamp;
             }
         }
     }
     if (fRescan && fRunScan && requests.size()) {
         int64_t scannedTime = pwallet->RescanFromTime(
             nLowestTimestamp, reserver, true /* update */);
         pwallet->ReacceptWalletTransactions();
 
         if (pwallet->IsAbortingRescan()) {
             throw JSONRPCError(RPC_MISC_ERROR, "Rescan aborted by user.");
         }
         if (scannedTime > nLowestTimestamp) {
             std::vector<UniValue> results = response.getValues();
             response.clear();
             response.setArray();
             size_t i = 0;
             for (const UniValue &request : requests.getValues()) {
                 // If key creation date is within the successfully scanned
                 // range, or if the import result already has an error set, let
                 // the result stand unmodified. Otherwise replace the result
                 // with an error message.
                 if (scannedTime <= GetImportTimestamp(request, now) ||
                     results.at(i).exists("error")) {
                     response.push_back(results.at(i));
                 } else {
                     UniValue result = UniValue(UniValue::VOBJ);
                     result.pushKV("success", UniValue(false));
                     result.pushKV(
                         "error",
                         JSONRPCError(
                             RPC_MISC_ERROR,
                             strprintf(
                                 "Rescan failed for key with creation timestamp "
                                 "%d. There was an error reading a block from "
                                 "time %d, which is after or within %d seconds "
                                 "of key creation, and could contain "
                                 "transactions pertaining to the key. As a "
                                 "result, transactions and coins using this key "
                                 "may not appear in the wallet. This error "
                                 "could be caused by pruning or data corruption "
                                 "(see bitcoind log for details) and could be "
                                 "dealt with by downloading and rescanning the "
                                 "relevant blocks (see -reindex and -rescan "
                                 "options).",
                                 GetImportTimestamp(request, now),
                                 scannedTime - TIMESTAMP_WINDOW - 1,
                                 TIMESTAMP_WINDOW)));
                     response.push_back(std::move(result));
                 }
                 ++i;
             }
         }
     }
 
     return response;
 }
 
 // clang-format off
 static const CRPCCommand commands[] = {
     //  category            name                        actor (function)          argNames
     //  ------------------- ------------------------    ----------------------    ----------
     { "wallet",             "abortrescan",              abortrescan,              {} },
     { "wallet",             "dumpprivkey",              dumpprivkey,              {"address"}  },
     { "wallet",             "dumpwallet",               dumpwallet,               {"filename"} },
     { "wallet",             "importmulti",              importmulti,              {"requests","options"} },
     { "wallet",             "importprivkey",            importprivkey,            {"privkey","label","rescan"} },
     { "wallet",             "importwallet",             importwallet,             {"filename"} },
     { "wallet",             "importaddress",            importaddress,            {"address","label","rescan","p2sh"} },
     { "wallet",             "importprunedfunds",        importprunedfunds,        {"rawtransaction","txoutproof"} },
     { "wallet",             "importpubkey",             importpubkey,             {"pubkey","label","rescan"} },
     { "wallet",             "removeprunedfunds",        removeprunedfunds,        {"txid"} },
 };
 // clang-format on
 
 void RegisterDumpRPCCommands(
     interfaces::Chain &chain,
     std::vector<std::unique_ptr<interfaces::Handler>> &handlers) {
     for (unsigned int vcidx = 0; vcidx < ARRAYLEN(commands); vcidx++) {
         handlers.emplace_back(chain.handleRpc(commands[vcidx]));
     }
 }
diff --git a/src/wallet/rpcwallet.cpp b/src/wallet/rpcwallet.cpp
index 4a1cc2bc3..0204d67ab 100644
--- a/src/wallet/rpcwallet.cpp
+++ b/src/wallet/rpcwallet.cpp
@@ -1,4887 +1,4816 @@
 // Copyright (c) 2010 Satoshi Nakamoto
 // Copyright (c) 2009-2018 The Bitcoin Core developers
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
 #include <amount.h>
 #include <chain.h>
 #include <chainparams.h> // for GetConsensus.
 #include <config.h>
 #include <consensus/validation.h>
 #include <core_io.h>
 #include <init.h>
 #include <interfaces/chain.h>
 #include <key_io.h>
 #include <net.h>
 #include <node/transaction.h>
 #include <outputtype.h>
 #include <policy/fees.h>
 #include <policy/policy.h>
 #include <rpc/mining.h>
 #include <rpc/rawtransaction_util.h>
 #include <rpc/server.h>
 #include <rpc/util.h>
 #include <script/descriptor.h>
 #include <shutdown.h>
 #include <timedata.h>
 #include <util/error.h>
 #include <util/moneystr.h>
 #include <util/system.h>
 #include <util/url.h>
 #include <util/validation.h>
 #include <validation.h>
 #include <wallet/coincontrol.h>
 #include <wallet/psbtwallet.h>
 #include <wallet/rpcwallet.h>
 #include <wallet/wallet.h>
 #include <wallet/walletdb.h>
 #include <wallet/walletutil.h>
 
 #include <univalue.h>
 
 #include <event2/http.h>
 
 #include <functional>
 
 static const std::string WALLET_ENDPOINT_BASE = "/wallet/";
 
 bool GetWalletNameFromJSONRPCRequest(const JSONRPCRequest &request,
                                      std::string &wallet_name) {
     if (request.URI.substr(0, WALLET_ENDPOINT_BASE.size()) ==
         WALLET_ENDPOINT_BASE) {
         // wallet endpoint was used
         wallet_name =
             urlDecode(request.URI.substr(WALLET_ENDPOINT_BASE.size()));
         return true;
     }
     return false;
 }
 
 std::shared_ptr<CWallet>
 GetWalletForJSONRPCRequest(const JSONRPCRequest &request) {
     std::string wallet_name;
     if (GetWalletNameFromJSONRPCRequest(request, wallet_name)) {
         std::shared_ptr<CWallet> pwallet = GetWallet(wallet_name);
         if (!pwallet) {
             throw JSONRPCError(
                 RPC_WALLET_NOT_FOUND,
                 "Requested wallet does not exist or is not loaded");
         }
         return pwallet;
     }
 
     std::vector<std::shared_ptr<CWallet>> wallets = GetWallets();
     return wallets.size() == 1 || (request.fHelp && wallets.size() > 0)
                ? wallets[0]
                : nullptr;
 }
 
 std::string HelpRequiringPassphrase(CWallet *const pwallet) {
     return pwallet && pwallet->IsCrypted()
                ? "\nRequires wallet passphrase to be set with walletpassphrase "
                  "call."
                : "";
 }
 
 bool EnsureWalletIsAvailable(CWallet *const pwallet, bool avoidException) {
     if (pwallet) {
         return true;
     }
     if (avoidException) {
         return false;
     }
     if (!HasWallets()) {
         throw JSONRPCError(RPC_METHOD_NOT_FOUND,
                            "Method not found (wallet method is disabled "
                            "because no wallet is loaded)");
     }
 
     throw JSONRPCError(RPC_WALLET_NOT_SPECIFIED,
                        "Wallet file not specified (must request wallet RPC "
                        "through /wallet/<filename> uri-path).");
 }
 
 void EnsureWalletIsUnlocked(CWallet *const pwallet) {
     if (pwallet->IsLocked()) {
         throw JSONRPCError(RPC_WALLET_UNLOCK_NEEDED,
                            "Error: Please enter the wallet passphrase with "
                            "walletpassphrase first.");
     }
 }
 
 static void WalletTxToJSON(interfaces::Chain &chain,
                            interfaces::Chain::Lock &locked_chain,
                            const CWalletTx &wtx, UniValue &entry) {
     int confirms = wtx.GetDepthInMainChain(locked_chain);
     entry.pushKV("confirmations", confirms);
     if (wtx.IsCoinBase()) {
         entry.pushKV("generated", true);
     }
     if (confirms > 0) {
         entry.pushKV("blockhash", wtx.hashBlock.GetHex());
         entry.pushKV("blockindex", wtx.nIndex);
         int64_t block_time;
         bool found_block =
             chain.findBlock(wtx.hashBlock, nullptr /* block */, &block_time);
         assert(found_block);
         entry.pushKV("blocktime", block_time);
     } else {
         entry.pushKV("trusted", wtx.IsTrusted(locked_chain));
     }
     uint256 hash = wtx.GetId();
     entry.pushKV("txid", hash.GetHex());
     UniValue conflicts(UniValue::VARR);
     for (const uint256 &conflict : wtx.GetConflicts()) {
         conflicts.push_back(conflict.GetHex());
     }
     entry.pushKV("walletconflicts", conflicts);
     entry.pushKV("time", wtx.GetTxTime());
     entry.pushKV("timereceived", (int64_t)wtx.nTimeReceived);
 
     for (const std::pair<const std::string, std::string> &item : wtx.mapValue) {
         entry.pushKV(item.first, item.second);
     }
 }
 
 static std::string LabelFromValue(const UniValue &value) {
     std::string label = value.get_str();
     if (label == "*") {
         throw JSONRPCError(RPC_WALLET_INVALID_LABEL_NAME, "Invalid label name");
     }
     return label;
 }
 
 static UniValue getnewaddress(const Config &config,
                               const JSONRPCRequest &request) {
     std::shared_ptr<CWallet> const wallet = GetWalletForJSONRPCRequest(request);
     CWallet *const pwallet = wallet.get();
 
     if (!EnsureWalletIsAvailable(pwallet, request.fHelp)) {
         return NullUniValue;
     }
 
     if (request.fHelp || request.params.size() > 2) {
         throw std::runtime_error(RPCHelpMan{
             "getnewaddress",
             "\nReturns a new Bitcoin address for receiving payments.\n"
             "If 'label' is specified, it is added to the address book \n"
             "so payments received with the address will be associated with "
             "'label'.\n",
             {
-                {"label", RPCArg::Type::STR, /* opt */ true,
-                 /* default_val */ "null",
+                {"label", RPCArg::Type::STR, /* default */ "null",
                  "The label name for the address to be linked to. If not "
                  "provided, the default label \"\" is used. It can also be set "
                  "to the empty string \"\" to represent the default label. The "
                  "label does not need to exist, it will be created if there is "
                  "no label by the given name."},
             },
             RPCResult{"\"address\"    (string) The new bitcoin address\n"},
             RPCExamples{HelpExampleCli("getnewaddress", "") +
                         HelpExampleRpc("getnewaddress", "")},
         }
                                      .ToString());
     }
 
     // Belt and suspenders check for disabled private keys
     if (pwallet->IsWalletFlagSet(WALLET_FLAG_DISABLE_PRIVATE_KEYS)) {
         throw JSONRPCError(RPC_WALLET_ERROR,
                            "Error: Private keys are disabled for this wallet");
     }
 
     LOCK(pwallet->cs_wallet);
 
     if (!pwallet->CanGetAddresses()) {
         throw JSONRPCError(RPC_WALLET_ERROR,
                            "Error: This wallet has no available keys");
     }
 
     // Parse the label first so we don't generate a key if there's an error
     std::string label;
     if (!request.params[0].isNull()) {
         label = LabelFromValue(request.params[0]);
     }
 
     OutputType output_type = pwallet->m_default_address_type;
     if (!request.params[1].isNull()) {
         if (!ParseOutputType(request.params[1].get_str(), output_type)) {
             throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY,
                                strprintf("Unknown address type '%s'",
                                          request.params[1].get_str()));
         }
     }
 
     if (!pwallet->IsLocked()) {
         pwallet->TopUpKeyPool();
     }
 
     // Generate a new key that is added to wallet
     CPubKey newKey;
     if (!pwallet->GetKeyFromPool(newKey)) {
         throw JSONRPCError(
             RPC_WALLET_KEYPOOL_RAN_OUT,
             "Error: Keypool ran out, please call keypoolrefill first");
     }
     pwallet->LearnRelatedScripts(newKey, output_type);
     CTxDestination dest = GetDestinationForKey(newKey, output_type);
 
     pwallet->SetAddressBook(dest, label, "receive");
 
     return EncodeDestination(dest, config);
 }
 
 static UniValue getrawchangeaddress(const Config &config,
                                     const JSONRPCRequest &request) {
     std::shared_ptr<CWallet> const wallet = GetWalletForJSONRPCRequest(request);
     CWallet *const pwallet = wallet.get();
 
     if (!EnsureWalletIsAvailable(pwallet, request.fHelp)) {
         return NullUniValue;
     }
 
     if (request.fHelp || request.params.size() > 1) {
         throw std::runtime_error(RPCHelpMan{
             "getrawchangeaddress",
             "\nReturns a new Bitcoin address, for receiving change.\n"
             "This is for use with raw transactions, NOT normal use.\n",
             {},
             RPCResult{"\"address\"    (string) The address\n"},
             RPCExamples{HelpExampleCli("getrawchangeaddress", "") +
                         HelpExampleRpc("getrawchangeaddress", "")},
         }
                                      .ToString());
     }
 
     // Belt and suspenders check for disabled private keys
     if (pwallet->IsWalletFlagSet(WALLET_FLAG_DISABLE_PRIVATE_KEYS)) {
         throw JSONRPCError(RPC_WALLET_ERROR,
                            "Error: Private keys are disabled for this wallet");
     }
 
     LOCK(pwallet->cs_wallet);
 
     if (!pwallet->CanGetAddresses(true)) {
         throw JSONRPCError(RPC_WALLET_ERROR,
                            "Error: This wallet has no available keys");
     }
 
     if (!pwallet->IsLocked()) {
         pwallet->TopUpKeyPool();
     }
 
     OutputType output_type =
         pwallet->m_default_change_type != OutputType::CHANGE_AUTO
             ? pwallet->m_default_change_type
             : pwallet->m_default_address_type;
     if (!request.params[0].isNull()) {
         if (!ParseOutputType(request.params[0].get_str(), output_type)) {
             throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY,
                                strprintf("Unknown address type '%s'",
                                          request.params[0].get_str()));
         }
     }
 
     CReserveKey reservekey(pwallet);
     CPubKey vchPubKey;
     if (!reservekey.GetReservedKey(vchPubKey, true)) {
         throw JSONRPCError(
             RPC_WALLET_KEYPOOL_RAN_OUT,
             "Error: Keypool ran out, please call keypoolrefill first");
     }
 
     reservekey.KeepKey();
 
     pwallet->LearnRelatedScripts(vchPubKey, output_type);
     CTxDestination dest = GetDestinationForKey(vchPubKey, output_type);
 
     return EncodeDestination(dest, config);
 }
 
 static UniValue setlabel(const Config &config, const JSONRPCRequest &request) {
     std::shared_ptr<CWallet> const wallet = GetWalletForJSONRPCRequest(request);
     CWallet *const pwallet = wallet.get();
 
     if (!EnsureWalletIsAvailable(pwallet, request.fHelp)) {
         return NullUniValue;
     }
 
     if (request.fHelp || request.params.size() != 2) {
         throw std::runtime_error(RPCHelpMan{
             "setlabel",
             "\nSets the label associated with the given address.\n",
             {
-                {"address", RPCArg::Type::STR, /* opt */ false,
-                 /* default_val */ "",
+                {"address", RPCArg::Type::STR, RPCArg::Optional::NO,
                  "The bitcoin address to be associated with a label."},
-                {"label", RPCArg::Type::STR, /* opt */ false,
-                 /* default_val */ "", "The label to assign to the address."},
+                {"label", RPCArg::Type::STR, RPCArg::Optional::NO,
+                 "The label to assign to the address."},
             },
             RPCResults{},
             RPCExamples{
                 HelpExampleCli(
                     "setlabel",
                     "\"1D1ZrZNe3JUo7ZycKEYQQiQAWd9y54F4XX\" \"tabby\"") +
                 HelpExampleRpc(
                     "setlabel",
                     "\"1D1ZrZNe3JUo7ZycKEYQQiQAWd9y54F4XX\", \"tabby\"")},
         }
                                      .ToString());
     }
     LOCK(pwallet->cs_wallet);
 
     CTxDestination dest =
         DecodeDestination(request.params[0].get_str(), config.GetChainParams());
     if (!IsValidDestination(dest)) {
         throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY,
                            "Invalid Bitcoin address");
     }
 
     std::string old_label = pwallet->mapAddressBook[dest].name;
     std::string label = LabelFromValue(request.params[1]);
 
     if (IsMine(*pwallet, dest)) {
         pwallet->SetAddressBook(dest, label, "receive");
     } else {
         pwallet->SetAddressBook(dest, label, "send");
     }
 
     return NullUniValue;
 }
 
 static CTransactionRef SendMoney(interfaces::Chain::Lock &locked_chain,
                                  CWallet *const pwallet,
                                  const CTxDestination &address, Amount nValue,
                                  bool fSubtractFeeFromAmount,
                                  mapValue_t mapValue) {
     Amount curBalance = pwallet->GetBalance();
 
     // Check amount
     if (nValue <= Amount::zero()) {
         throw JSONRPCError(RPC_INVALID_PARAMETER, "Invalid amount");
     }
 
     if (nValue > curBalance) {
         throw JSONRPCError(RPC_WALLET_INSUFFICIENT_FUNDS, "Insufficient funds");
     }
 
     if (pwallet->GetBroadcastTransactions() && !pwallet->chain().p2pEnabled()) {
         throw JSONRPCError(
             RPC_CLIENT_P2P_DISABLED,
             "Error: Peer-to-peer functionality missing or disabled");
     }
 
     // Parse Bitcoin address
     CScript scriptPubKey = GetScriptForDestination(address);
 
     // Create and send the transaction
     CReserveKey reservekey(pwallet);
     Amount nFeeRequired;
     std::string strError;
     std::vector<CRecipient> vecSend;
     int nChangePosRet = -1;
     CRecipient recipient = {scriptPubKey, nValue, fSubtractFeeFromAmount};
     vecSend.push_back(recipient);
 
     CCoinControl coinControl;
     CTransactionRef tx;
     if (!pwallet->CreateTransaction(locked_chain, vecSend, tx, reservekey,
                                     nFeeRequired, nChangePosRet, strError,
                                     coinControl)) {
         if (!fSubtractFeeFromAmount && nValue + nFeeRequired > curBalance) {
             strError = strprintf("Error: This transaction requires a "
                                  "transaction fee of at least %s",
                                  FormatMoney(nFeeRequired));
         }
         throw JSONRPCError(RPC_WALLET_ERROR, strError);
     }
     CValidationState state;
     if (!pwallet->CommitTransaction(tx, std::move(mapValue), {} /* orderForm */,
                                     reservekey, state)) {
         strError =
             strprintf("Error: The transaction was rejected! Reason given: %s",
                       FormatStateMessage(state));
         throw JSONRPCError(RPC_WALLET_ERROR, strError);
     }
     return tx;
 }
 
 static UniValue sendtoaddress(const Config &config,
                               const JSONRPCRequest &request) {
     std::shared_ptr<CWallet> const wallet = GetWalletForJSONRPCRequest(request);
     CWallet *const pwallet = wallet.get();
 
     if (!EnsureWalletIsAvailable(pwallet, request.fHelp)) {
         return NullUniValue;
     }
 
     if (request.fHelp || request.params.size() < 2 ||
         request.params.size() > 5) {
         throw std::runtime_error(RPCHelpMan{
             "sendtoaddress",
             "\nSend an amount to a given address.\n" +
                 HelpRequiringPassphrase(pwallet) + "\n",
             {
-                {"address", RPCArg::Type::STR, /* opt */ false,
-                 /* default_val */ "", "The bitcoin address to send to."},
-                {"amount", RPCArg::Type::AMOUNT, /* opt */ false,
-                 /* default_val */ "",
+                {"address", RPCArg::Type::STR, RPCArg::Optional::NO,
+                 "The bitcoin address to send to."},
+                {"amount", RPCArg::Type::AMOUNT, RPCArg::Optional::NO,
                  "The amount in " + CURRENCY_UNIT + " to send. eg 0.1"},
-                {"comment", RPCArg::Type::STR, /* opt */ true,
-                 /* default_val */ "null",
+                {"comment", RPCArg::Type::STR,
+                 RPCArg::Optional::OMITTED_NAMED_ARG,
                  "A comment used to store what the transaction is for.\n"
                  "                             This is not part of the "
                  "transaction, just kept in your wallet."},
-                {"comment_to", RPCArg::Type::STR, /* opt */ true,
-                 /* default_val */ "null",
+                {"comment_to", RPCArg::Type::STR,
+                 RPCArg::Optional::OMITTED_NAMED_ARG,
                  "A comment to store the name of the person or organization\n"
                  "                             to which you're sending the "
                  "transaction. This is not part of the \n"
                  "                             transaction, just kept in "
                  "your wallet."},
                 {"subtractfeefromamount", RPCArg::Type::BOOL,
-                 /* opt */ true, /* default_val */ "false",
+                 /* default */ "false",
                  "The fee will be deducted from the amount being sent.\n"
                  "                             The recipient will receive "
                  "less bitcoins than you enter in the amount field."},
             },
             RPCResult{
                 "\"txid\"                  (string) The transaction id.\n"},
             RPCExamples{
                 HelpExampleCli("sendtoaddress",
                                "\"1M72Sfpbz1BPpXFHz9m3CdqATR44Jvaydd\" 0.1") +
                 HelpExampleCli("sendtoaddress",
                                "\"1M72Sfpbz1BPpXFHz9m3CdqATR44Jvay"
                                "dd\" 0.1 \"donation\" \"seans "
                                "outpost\"") +
                 HelpExampleCli("sendtoaddress", "\"1M72Sfpbz1BPpXFHz9m3CdqATR44"
                                                 "Jvaydd\" 0.1 \"\" \"\" true") +
                 HelpExampleRpc("sendtoaddress",
                                "\"1M72Sfpbz1BPpXFHz9m3CdqATR44Jvay"
                                "dd\", 0.1, \"donation\", \"seans "
                                "outpost\"")},
         }
                                      .ToString());
     }
 
     // Make sure the results are valid at least up to the most recent block
     // the user could have gotten from another RPC command prior to now
     pwallet->BlockUntilSyncedToCurrentChain();
 
     auto locked_chain = pwallet->chain().lock();
     LOCK(pwallet->cs_wallet);
 
     CTxDestination dest =
         DecodeDestination(request.params[0].get_str(), config.GetChainParams());
     if (!IsValidDestination(dest)) {
         throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Invalid address");
     }
 
     // Amount
     Amount nAmount = AmountFromValue(request.params[1]);
     if (nAmount <= Amount::zero()) {
         throw JSONRPCError(RPC_TYPE_ERROR, "Invalid amount for send");
     }
 
     // Wallet comments
     mapValue_t mapValue;
     if (!request.params[2].isNull() && !request.params[2].get_str().empty()) {
         mapValue["comment"] = request.params[2].get_str();
     }
     if (!request.params[3].isNull() && !request.params[3].get_str().empty()) {
         mapValue["to"] = request.params[3].get_str();
     }
 
     bool fSubtractFeeFromAmount = false;
     if (!request.params[4].isNull()) {
         fSubtractFeeFromAmount = request.params[4].get_bool();
     }
 
     EnsureWalletIsUnlocked(pwallet);
 
     CTransactionRef tx = SendMoney(*locked_chain, pwallet, dest, nAmount,
                                    fSubtractFeeFromAmount, std::move(mapValue));
     return tx->GetId().GetHex();
 }
 
 static UniValue listaddressgroupings(const Config &config,
                                      const JSONRPCRequest &request) {
     std::shared_ptr<CWallet> const wallet = GetWalletForJSONRPCRequest(request);
     CWallet *const pwallet = wallet.get();
 
     if (!EnsureWalletIsAvailable(pwallet, request.fHelp)) {
         return NullUniValue;
     }
 
     if (request.fHelp || request.params.size() != 0) {
         throw std::runtime_error(RPCHelpMan{
             "listaddressgroupings",
             "\nLists groups of addresses which have had their "
             "common ownership\n"
             "made public by common use as inputs or as the "
             "resulting change\n"
             "in past transactions\n",
             {},
             RPCResult{
                 "[\n"
                 "  [\n"
                 "    [\n"
                 "      \"address\",            (string) The bitcoin address\n"
                 "      amount,                 (numeric) The amount in " +
                 CURRENCY_UNIT +
                 "\n"
                 "      \"label\"               (string, optional) The label\n"
                 "    ]\n"
                 "    ,...\n"
                 "  ]\n"
                 "  ,...\n"
                 "]\n"},
             RPCExamples{HelpExampleCli("listaddressgroupings", "") +
                         HelpExampleRpc("listaddressgroupings", "")},
         }
                                      .ToString());
     }
 
     // Make sure the results are valid at least up to the most recent block
     // the user could have gotten from another RPC command prior to now
     pwallet->BlockUntilSyncedToCurrentChain();
 
     auto locked_chain = pwallet->chain().lock();
     LOCK(pwallet->cs_wallet);
 
     UniValue jsonGroupings(UniValue::VARR);
     std::map<CTxDestination, Amount> balances =
         pwallet->GetAddressBalances(*locked_chain);
     for (const std::set<CTxDestination> &grouping :
          pwallet->GetAddressGroupings()) {
         UniValue jsonGrouping(UniValue::VARR);
         for (const CTxDestination &address : grouping) {
             UniValue addressInfo(UniValue::VARR);
             addressInfo.push_back(EncodeDestination(address, config));
             addressInfo.push_back(ValueFromAmount(balances[address]));
 
             if (pwallet->mapAddressBook.find(address) !=
                 pwallet->mapAddressBook.end()) {
                 addressInfo.push_back(
                     pwallet->mapAddressBook.find(address)->second.name);
             }
             jsonGrouping.push_back(addressInfo);
         }
         jsonGroupings.push_back(jsonGrouping);
     }
 
     return jsonGroupings;
 }
 
 static UniValue signmessage(const Config &config,
                             const JSONRPCRequest &request) {
     std::shared_ptr<CWallet> const wallet = GetWalletForJSONRPCRequest(request);
     CWallet *const pwallet = wallet.get();
 
     if (!EnsureWalletIsAvailable(pwallet, request.fHelp)) {
         return NullUniValue;
     }
 
     if (request.fHelp || request.params.size() != 2) {
         throw std::runtime_error(RPCHelpMan{
             "signmessage",
             "\nSign a message with the private key of an address" +
                 HelpRequiringPassphrase(pwallet) + "\n",
             {
-                {"address", RPCArg::Type::STR, /* opt */ false,
-                 /* default_val */ "",
+                {"address", RPCArg::Type::STR, RPCArg::Optional::NO,
                  "The bitcoin address to use for the private key."},
-                {"message", RPCArg::Type::STR, /* opt */ false,
-                 /* default_val */ "", "The message to create a signature of."},
+                {"message", RPCArg::Type::STR, RPCArg::Optional::NO,
+                 "The message to create a signature of."},
             },
             RPCResult{
                 "\"signature\"          (string) The signature of the message "
                 "encoded in base 64\n"},
             RPCExamples{
                 "\nUnlock the wallet for 30 seconds\n" +
                 HelpExampleCli("walletpassphrase", "\"mypassphrase\" 30") +
                 "\nCreate the signature\n" +
                 HelpExampleCli(
                     "signmessage",
                     "\"1D1ZrZNe3JUo7ZycKEYQQiQAWd9y54F4XX\" \"my message\"") +
                 "\nVerify the signature\n" +
                 HelpExampleCli("verifymessage",
                                "\"1D1ZrZNe3JUo7ZycKEYQQiQAWd9y54F4"
                                "XX\" \"signature\" \"my "
                                "message\"") +
                 "\nAs a JSON-RPC call\n" +
                 HelpExampleRpc(
                     "signmessage",
                     "\"1D1ZrZNe3JUo7ZycKEYQQiQAWd9y54F4XX\", \"my message\"")},
         }
                                      .ToString());
     }
 
     auto locked_chain = pwallet->chain().lock();
     LOCK(pwallet->cs_wallet);
 
     EnsureWalletIsUnlocked(pwallet);
 
     std::string strAddress = request.params[0].get_str();
     std::string strMessage = request.params[1].get_str();
 
     CTxDestination dest =
         DecodeDestination(strAddress, config.GetChainParams());
     if (!IsValidDestination(dest)) {
         throw JSONRPCError(RPC_TYPE_ERROR, "Invalid address");
     }
 
     const CKeyID *keyID = boost::get<CKeyID>(&dest);
     if (!keyID) {
         throw JSONRPCError(RPC_TYPE_ERROR, "Address does not refer to key");
     }
 
     CKey key;
     if (!pwallet->GetKey(*keyID, key)) {
         throw JSONRPCError(RPC_WALLET_ERROR, "Private key not available");
     }
 
     CHashWriter ss(SER_GETHASH, 0);
     ss << strMessageMagic;
     ss << strMessage;
 
     std::vector<uint8_t> vchSig;
     if (!key.SignCompact(ss.GetHash(), vchSig)) {
         throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Sign failed");
     }
 
     return EncodeBase64(vchSig.data(), vchSig.size());
 }
 
 static UniValue getreceivedbyaddress(const Config &config,
                                      const JSONRPCRequest &request) {
     std::shared_ptr<CWallet> const wallet = GetWalletForJSONRPCRequest(request);
     CWallet *const pwallet = wallet.get();
 
     if (!EnsureWalletIsAvailable(pwallet, request.fHelp)) {
         return NullUniValue;
     }
 
     if (request.fHelp || request.params.size() < 1 ||
         request.params.size() > 2) {
         throw std::runtime_error(RPCHelpMan{
             "getreceivedbyaddress",
             "\nReturns the total amount received by the given address in "
             "transactions with at least minconf confirmations.\n",
             {
-                {"address", RPCArg::Type::STR, /* opt */ false,
-                 /* default_val */ "", "The bitcoin address for transactions."},
-                {"minconf", RPCArg::Type::NUM, /* opt */ true,
-                 /* default_val */ "1",
+                {"address", RPCArg::Type::STR, RPCArg::Optional::NO,
+                 "The bitcoin address for transactions."},
+                {"minconf", RPCArg::Type::NUM, /* default */ "1",
                  "Only include transactions confirmed at least this many "
                  "times."},
             },
             RPCResult{"amount   (numeric) The total amount in " +
                       CURRENCY_UNIT + " received at this address.\n"},
             RPCExamples{
                 "\nThe amount from transactions with at least 1 "
                 "confirmation\n" +
                 HelpExampleCli("getreceivedbyaddress",
                                "\"1D1ZrZNe3JUo7ZycKEYQQiQAWd9y54F4XX\"") +
                 "\nThe amount including unconfirmed transactions, zero "
                 "confirmations\n" +
                 HelpExampleCli("getreceivedbyaddress",
                                "\"1D1ZrZNe3JUo7ZycKEYQQiQAWd9y54F4XX\" 0") +
                 "\nThe amount with at least 6 confirmations\n" +
                 HelpExampleCli("getreceivedbyaddress",
                                "\"1D1ZrZNe3JUo7ZycKEYQQiQAWd9y54F4XX\" 6") +
                 "\nAs a JSON-RPC call\n" +
                 HelpExampleRpc("getreceivedbyaddress",
                                "\"1D1ZrZNe3JUo7ZycKEYQQiQAWd9y54F4XX\", 6")},
         }
                                      .ToString());
     }
 
     // Make sure the results are valid at least up to the most recent block
     // the user could have gotten from another RPC command prior to now
     pwallet->BlockUntilSyncedToCurrentChain();
 
     auto locked_chain = pwallet->chain().lock();
     LOCK(pwallet->cs_wallet);
 
     // Bitcoin address
     CTxDestination dest =
         DecodeDestination(request.params[0].get_str(), config.GetChainParams());
     if (!IsValidDestination(dest)) {
         throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY,
                            "Invalid Bitcoin address");
     }
     CScript scriptPubKey = GetScriptForDestination(dest);
     if (!IsMine(*pwallet, scriptPubKey)) {
         throw JSONRPCError(RPC_WALLET_ERROR, "Address not found in wallet");
     }
 
     // Minimum confirmations
     int nMinDepth = 1;
     if (!request.params[1].isNull()) {
         nMinDepth = request.params[1].get_int();
     }
 
     // Tally
     Amount nAmount = Amount::zero();
     for (const std::pair<const TxId, CWalletTx> &pairWtx : pwallet->mapWallet) {
         const CWalletTx &wtx = pairWtx.second;
 
         CValidationState state;
         if (wtx.IsCoinBase() ||
             !locked_chain->contextualCheckTransactionForCurrentBlock(
                 config.GetChainParams().GetConsensus(), *wtx.tx, state)) {
             continue;
         }
 
         for (const CTxOut &txout : wtx.tx->vout) {
             if (txout.scriptPubKey == scriptPubKey) {
                 if (wtx.GetDepthInMainChain(*locked_chain) >= nMinDepth) {
                     nAmount += txout.nValue;
                 }
             }
         }
     }
 
     return ValueFromAmount(nAmount);
 }
 
 static UniValue getreceivedbylabel(const Config &config,
                                    const JSONRPCRequest &request) {
     std::shared_ptr<CWallet> const wallet = GetWalletForJSONRPCRequest(request);
     CWallet *const pwallet = wallet.get();
 
     if (!EnsureWalletIsAvailable(pwallet, request.fHelp)) {
         return NullUniValue;
     }
 
     if (request.fHelp || request.params.size() < 1 ||
         request.params.size() > 2) {
         throw std::runtime_error(RPCHelpMan{
             "getreceivedbylabel",
             "\nReturns the total amount received by addresses with <label> "
             "in transactions with at least [minconf] confirmations.\n",
             {
-                {"label", RPCArg::Type::STR, /* opt */ false,
-                 /* default_val */ "",
+                {"label", RPCArg::Type::STR, RPCArg::Optional::NO,
                  "The selected label, may be the default label "
                  "using \"\"."},
-                {"minconf", RPCArg::Type::NUM, /* opt */ true,
-                 /* default_val */ "1",
+                {"minconf", RPCArg::Type::NUM, /* default */ "1",
                  "Only include transactions confirmed at least this "
                  "many times."},
             },
             RPCResult{"amount              (numeric) The total amount in " +
                       CURRENCY_UNIT + " received for this label.\n"},
             RPCExamples{
                 "\nAmount received by the default label with at least 1 "
                 "confirmation\n" +
                 HelpExampleCli("getreceivedbylabel", "\"\"") +
                 "\nAmount received at the tabby label including unconfirmed "
                 "amounts with zero confirmations\n" +
                 HelpExampleCli("getreceivedbylabel", "\"tabby\" 0") +
                 "\nThe amount with at least 6 confirmations\n" +
                 HelpExampleCli("getreceivedbylabel", "\"tabby\" 6") +
                 "\nAs a JSON-RPC call\n" +
                 HelpExampleRpc("getreceivedbylabel", "\"tabby\", 6")},
         }
                                      .ToString());
     }
 
     // Make sure the results are valid at least up to the most recent block
     // the user could have gotten from another RPC command prior to now
     pwallet->BlockUntilSyncedToCurrentChain();
 
     auto locked_chain = pwallet->chain().lock();
     LOCK(pwallet->cs_wallet);
 
     // Minimum confirmations
     int nMinDepth = 1;
     if (!request.params[1].isNull()) {
         nMinDepth = request.params[1].get_int();
     }
 
     // Get the set of pub keys assigned to label
     std::string label = LabelFromValue(request.params[0]);
     std::set<CTxDestination> setAddress = pwallet->GetLabelAddresses(label);
 
     // Tally
     Amount nAmount = Amount::zero();
     for (const std::pair<const TxId, CWalletTx> &pairWtx : pwallet->mapWallet) {
         const CWalletTx &wtx = pairWtx.second;
         CValidationState state;
         if (wtx.IsCoinBase() ||
             !locked_chain->contextualCheckTransactionForCurrentBlock(
                 config.GetChainParams().GetConsensus(), *wtx.tx, state)) {
             continue;
         }
 
         for (const CTxOut &txout : wtx.tx->vout) {
             CTxDestination address;
             if (ExtractDestination(txout.scriptPubKey, address) &&
                 IsMine(*pwallet, address) && setAddress.count(address)) {
                 if (wtx.GetDepthInMainChain(*locked_chain) >= nMinDepth) {
                     nAmount += txout.nValue;
                 }
             }
         }
     }
 
     return ValueFromAmount(nAmount);
 }
 
 static UniValue getbalance(const Config &config,
                            const JSONRPCRequest &request) {
     std::shared_ptr<CWallet> const wallet = GetWalletForJSONRPCRequest(request);
     CWallet *const pwallet = wallet.get();
 
     if (!EnsureWalletIsAvailable(pwallet, request.fHelp)) {
         return NullUniValue;
     }
 
     if (request.fHelp || (request.params.size() > 3)) {
         throw std::runtime_error(RPCHelpMan{
             "getbalance",
             "\nReturns the total available balance.\n"
             "The available balance is what the wallet considers "
             "currently spendable, and is\n"
             "thus affected by options which limit spendability such "
             "as -spendzeroconfchange.\n",
             {
-                {"dummy", RPCArg::Type::STR, /* opt */ true,
-                 /* default_val */ "null",
+                {"dummy", RPCArg::Type::STR,
+                 RPCArg::Optional::OMITTED_NAMED_ARG,
                  "Remains for backward compatibility. Must be excluded or set "
                  "to \"*\"."},
-                {"minconf", RPCArg::Type::NUM, /* opt */ true,
-                 /* default_val */ "0",
+                {"minconf", RPCArg::Type::NUM, /* default */ "0",
                  "Only include transactions confirmed at least this "
                  "many times."},
                 {"include_watchonly", RPCArg::Type::BOOL,
-                 /* opt */ true, /* default_val */ "false",
+                 /* default */ "false",
                  "Also include balance in watch-only addresses (see "
                  "'importaddress')"},
             },
             RPCResult{"amount              (numeric) The total amount in " +
                       CURRENCY_UNIT + " received for this wallet.\n"},
             RPCExamples{"\nThe total amount in the wallet with 1 or more "
                         "confirmations\n" +
                         HelpExampleCli("getbalance", "") +
                         "\nThe total amount in the wallet at least 6 blocks "
                         "confirmed\n" +
                         HelpExampleCli("getbalance", "\"*\" 6") +
                         "\nAs a JSON-RPC call\n" +
                         HelpExampleRpc("getbalance", "\"*\", 6")},
         }
                                      .ToString());
     }
 
     // Make sure the results are valid at least up to the most recent block
     // the user could have gotten from another RPC command prior to now
     pwallet->BlockUntilSyncedToCurrentChain();
 
     auto locked_chain = pwallet->chain().lock();
     LOCK(pwallet->cs_wallet);
 
     const UniValue &dummy_value = request.params[0];
     if (!dummy_value.isNull() && dummy_value.get_str() != "*") {
         throw JSONRPCError(
             RPC_METHOD_DEPRECATED,
             "dummy first argument must be excluded or set to \"*\".");
     }
 
     int min_depth = 0;
     if (!request.params[1].isNull()) {
         min_depth = request.params[1].get_int();
     }
 
     isminefilter filter = ISMINE_SPENDABLE;
     if (!request.params[2].isNull() && request.params[2].get_bool()) {
         filter = filter | ISMINE_WATCH_ONLY;
     }
 
     return ValueFromAmount(pwallet->GetBalance(filter, min_depth));
 }
 
 static UniValue getunconfirmedbalance(const Config &config,
                                       const JSONRPCRequest &request) {
     std::shared_ptr<CWallet> const wallet = GetWalletForJSONRPCRequest(request);
     CWallet *const pwallet = wallet.get();
 
     if (!EnsureWalletIsAvailable(pwallet, request.fHelp)) {
         return NullUniValue;
     }
 
     if (request.fHelp || request.params.size() > 0) {
         throw std::runtime_error(RPCHelpMan{
             "getunconfirmedbalance",
             "Returns the server's total unconfirmed balance\n",
             {},
             RPCResults{},
             RPCExamples{""},
         }
                                      .ToString());
     }
 
     // Make sure the results are valid at least up to the most recent block
     // the user could have gotten from another RPC command prior to now
     pwallet->BlockUntilSyncedToCurrentChain();
 
     auto locked_chain = pwallet->chain().lock();
     LOCK(pwallet->cs_wallet);
 
     return ValueFromAmount(pwallet->GetUnconfirmedBalance());
 }
 
 static UniValue sendmany(const Config &config, const JSONRPCRequest &request) {
     std::shared_ptr<CWallet> const wallet = GetWalletForJSONRPCRequest(request);
     CWallet *const pwallet = wallet.get();
 
     if (!EnsureWalletIsAvailable(pwallet, request.fHelp)) {
         return NullUniValue;
     }
 
     if (request.fHelp || request.params.size() < 2 ||
         request.params.size() > 5) {
         throw std::runtime_error(RPCHelpMan{
             "sendmany",
             "\nSend multiple times. Amounts are double-precision "
             "floating point numbers." +
                 HelpRequiringPassphrase(pwallet) + "\n",
             {
-                {"dummy", RPCArg::Type::STR, /* opt */ false,
-                 /* default_val */ "",
+                {"dummy", RPCArg::Type::STR, RPCArg::Optional::NO,
                  "Must be set to \"\" for backwards compatibility.", "\"\""},
                 {
                     "amounts",
                     RPCArg::Type::OBJ,
-                    /* opt */ false,
-                    /* default_val */ "",
+                    RPCArg::Optional::NO,
                     "A json object with addresses and amounts",
                     {
-                        {"address", RPCArg::Type::AMOUNT, /* opt */ false,
-                         /* default_val */ "",
+                        {"address", RPCArg::Type::AMOUNT, RPCArg::Optional::NO,
                          "The bitcoin address is the key, the numeric "
                          "amount (can be string) in " +
                              CURRENCY_UNIT + " is the value"},
                     },
                 },
-                {"minconf", RPCArg::Type::NUM, /* opt */ true,
-                 /* default_val */ "1",
+                {"minconf", RPCArg::Type::NUM, /* default */ "1",
                  "Only use the balance confirmed at least this many "
                  "times."},
-                {"comment", RPCArg::Type::STR, /* opt */ true,
-                 /* default_val */ "null", "A comment"},
+                {"comment", RPCArg::Type::STR,
+                 RPCArg::Optional::OMITTED_NAMED_ARG, "A comment"},
                 {
                     "subtractfeefrom",
                     RPCArg::Type::ARR,
-                    /* opt */ true,
-                    /* default_val */ "null",
+                    RPCArg::Optional::OMITTED_NAMED_ARG,
                     "A json array with addresses.\n"
                     "                           The fee will be equally "
                     "deducted from the amount of each selected address.\n"
                     "                           Those recipients will "
                     "receive less bitcoins than you enter in their "
                     "corresponding amount field.\n"
                     "                           If no addresses are "
                     "specified here, the sender pays the fee.",
                     {
-                        {"address", RPCArg::Type::STR, /* opt */ true,
-                         /* default_val */ "",
+                        {"address", RPCArg::Type::STR,
+                         RPCArg::Optional::OMITTED,
                          "Subtract fee from this address"},
                     },
                 },
             },
             RPCResult{
                 "\"txid\"                   (string) The transaction id for "
                 "the send. Only 1 transaction is created regardless of \n"
                 "                                    the number of "
                 "addresses.\n"},
             RPCExamples{
                 "\nSend two amounts to two different addresses:\n" +
                 HelpExampleCli(
                     "sendmany",
                     "\"\" "
                     "\"{\\\"1D1ZrZNe3JUo7ZycKEYQQiQAWd9y54F4XX\\\":0.01,"
                     "\\\"1353tsE8YMTA4EuV7dgUXGjNFf9KpVvKHz\\\":0.02}"
                     "\"") +
                 "\nSend two amounts to two different addresses setting the "
                 "confirmation and comment:\n" +
                 HelpExampleCli(
                     "sendmany",
                     "\"\" "
                     "\"{\\\"1D1ZrZNe3JUo7ZycKEYQQiQAWd9y54F4XX\\\":0.01,"
                     "\\\"1353tsE8YMTA4EuV7dgUXGjNFf9KpVvKHz\\\":0.02}\" "
                     "6 \"testing\"") +
                 "\nSend two amounts to two different addresses, subtract fee "
                 "from amount:\n" +
                 HelpExampleCli(
                     "sendmany",
                     "\"\" "
                     "\"{\\\"1D1ZrZNe3JUo7ZycKEYQQiQAWd9y54F4XX\\\":0.01,"
                     "\\\"1353tsE8YMTA4EuV7dgUXGjNFf9KpVvKHz\\\":0.02}\" "
                     "1 \"\" "
                     "\"[\\\"1D1ZrZNe3JUo7ZycKEYQQiQAWd9y54F4XX\\\","
                     "\\\"1353tsE8YMTA4EuV7dgUXGjNFf9KpVvKHz\\\"]\"") +
                 "\nAs a JSON-RPC call\n" +
                 HelpExampleRpc(
                     "sendmany",
                     "\"\", "
                     "\"{\\\"1D1ZrZNe3JUo7ZycKEYQQiQAWd9y54F4XX\\\":0.01,"
                     "\\\"1353tsE8YMTA4EuV7dgUXGjNFf9KpVvKHz\\\":0.02}\","
                     " 6, \"testing\"")},
         }
                                      .ToString());
     }
 
     // Make sure the results are valid at least up to the most recent block
     // the user could have gotten from another RPC command prior to now
     pwallet->BlockUntilSyncedToCurrentChain();
 
     auto locked_chain = pwallet->chain().lock();
     LOCK(pwallet->cs_wallet);
 
     if (pwallet->GetBroadcastTransactions() && !pwallet->chain().p2pEnabled()) {
         throw JSONRPCError(
             RPC_CLIENT_P2P_DISABLED,
             "Error: Peer-to-peer functionality missing or disabled");
     }
 
     if (!request.params[0].isNull() && !request.params[0].get_str().empty()) {
         throw JSONRPCError(RPC_INVALID_PARAMETER,
                            "Dummy value must be set to \"\"");
     }
     UniValue sendTo = request.params[1].get_obj();
     int nMinDepth = 1;
     if (!request.params[2].isNull()) {
         nMinDepth = request.params[2].get_int();
     }
 
     mapValue_t mapValue;
     if (!request.params[3].isNull() && !request.params[3].get_str().empty()) {
         mapValue["comment"] = request.params[3].get_str();
     }
 
     UniValue subtractFeeFromAmount(UniValue::VARR);
     if (!request.params[4].isNull()) {
         subtractFeeFromAmount = request.params[4].get_array();
     }
 
     std::set<CTxDestination> destinations;
     std::vector<CRecipient> vecSend;
 
     Amount totalAmount = Amount::zero();
     std::vector<std::string> keys = sendTo.getKeys();
     for (const std::string &name_ : keys) {
         CTxDestination dest = DecodeDestination(name_, config.GetChainParams());
         if (!IsValidDestination(dest)) {
             throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY,
                                std::string("Invalid Bitcoin address: ") +
                                    name_);
         }
 
         if (destinations.count(dest)) {
             throw JSONRPCError(
                 RPC_INVALID_PARAMETER,
                 std::string("Invalid parameter, duplicated address: ") + name_);
         }
         destinations.insert(dest);
 
         CScript scriptPubKey = GetScriptForDestination(dest);
         Amount nAmount = AmountFromValue(sendTo[name_]);
         if (nAmount <= Amount::zero()) {
             throw JSONRPCError(RPC_TYPE_ERROR, "Invalid amount for send");
         }
         totalAmount += nAmount;
 
         bool fSubtractFeeFromAmount = false;
         for (size_t idx = 0; idx < subtractFeeFromAmount.size(); idx++) {
             const UniValue &addr = subtractFeeFromAmount[idx];
             if (addr.get_str() == name_) {
                 fSubtractFeeFromAmount = true;
             }
         }
 
         CRecipient recipient = {scriptPubKey, nAmount, fSubtractFeeFromAmount};
         vecSend.push_back(recipient);
     }
 
     EnsureWalletIsUnlocked(pwallet);
 
     // Check funds
     if (totalAmount > pwallet->GetLegacyBalance(ISMINE_SPENDABLE, nMinDepth)) {
         throw JSONRPCError(RPC_WALLET_INSUFFICIENT_FUNDS,
                            "Wallet has insufficient funds");
     }
 
     // Shuffle recipient list
     std::shuffle(vecSend.begin(), vecSend.end(), FastRandomContext());
 
     // Send
     CReserveKey keyChange(pwallet);
     Amount nFeeRequired = Amount::zero();
     int nChangePosRet = -1;
     std::string strFailReason;
     CTransactionRef tx;
     CCoinControl coinControl;
     bool fCreated = pwallet->CreateTransaction(
         *locked_chain, vecSend, tx, keyChange, nFeeRequired, nChangePosRet,
         strFailReason, coinControl);
     if (!fCreated) {
         throw JSONRPCError(RPC_WALLET_INSUFFICIENT_FUNDS, strFailReason);
     }
     CValidationState state;
     if (!pwallet->CommitTransaction(tx, std::move(mapValue), {} /* orderForm */,
                                     keyChange, state)) {
         strFailReason = strprintf("Transaction commit failed:: %s",
                                   FormatStateMessage(state));
         throw JSONRPCError(RPC_WALLET_ERROR, strFailReason);
     }
 
     return tx->GetId().GetHex();
 }
 
 static UniValue addmultisigaddress(const Config &config,
                                    const JSONRPCRequest &request) {
     std::shared_ptr<CWallet> const wallet = GetWalletForJSONRPCRequest(request);
     CWallet *const pwallet = wallet.get();
 
     if (!EnsureWalletIsAvailable(pwallet, request.fHelp)) {
         return NullUniValue;
     }
 
     if (request.fHelp || request.params.size() < 2 ||
         request.params.size() > 3) {
         std::string msg =
             RPCHelpMan{
                 "addmultisigaddress",
                 "\nAdd a nrequired-to-sign multisignature address to the "
                 "wallet. "
                 "Requires a new wallet backup.\n"
                 "Each key is a Bitcoin address or hex-encoded public key.\n"
                 "If 'label' is specified (DEPRECATED), assign address to that "
                 "label.\n",
                 {
-                    {"nrequired", RPCArg::Type::NUM, /* opt */ false,
-                     /* default_val */ "",
+                    {"nrequired", RPCArg::Type::NUM, RPCArg::Optional::NO,
                      "The number of required signatures out of the n keys or "
                      "addresses."},
                     {
                         "keys",
                         RPCArg::Type::ARR,
-                        /* opt */ false,
-                        /* default_val */ "",
+                        RPCArg::Optional::NO,
                         "A json array of bitcoin addresses or hex-encoded "
                         "public keys",
                         {
-                            {"key", RPCArg::Type::STR, /* opt */ false,
-                             /* default_val */ "",
+                            {"key", RPCArg::Type::STR,
+                             RPCArg::Optional::OMITTED,
                              "bitcoin address or hex-encoded public key"},
                         },
                     },
-                    {"label", RPCArg::Type::STR, /* opt */ true,
-                     /* default_val */ "null",
+                    {"label", RPCArg::Type::STR,
+                     RPCArg::Optional::OMITTED_NAMED_ARG,
                      "A label to assign the addresses to."},
                 },
                 RPCResult{"{\n"
                           "  \"address\":\"multisigaddress\",    (string) The "
                           "value of the new multisig address.\n"
                           "  \"redeemScript\":\"script\"         (string) The "
                           "string value of the hex-encoded redemption script.\n"
                           "}\n"},
                 RPCExamples{
                     "\nAdd a multisig address from 2 addresses\n" +
                     HelpExampleCli(
                         "addmultisigaddress",
                         "2 "
                         "\"[\\\"16sSauSf5pF2UkUwvKGq4qjNRzBZYqgEL5\\\","
                         "\\\"171sgjn4YtPu27adkKGrdDwzRTxnRkBfKV\\\"]\"") +
                     "\nAs a JSON-RPC call\n" +
                     HelpExampleRpc(
                         "addmultisigaddress",
                         "2, "
                         "\"[\\\"16sSauSf5pF2UkUwvKGq4qjNRzBZYqgEL5\\\","
                         "\\\"171sgjn4YtPu27adkKGrdDwzRTxnRkBfKV\\\"]\"")},
             }
                 .ToString();
         throw std::runtime_error(msg);
     }
 
     auto locked_chain = pwallet->chain().lock();
     LOCK(pwallet->cs_wallet);
 
     std::string label;
     if (!request.params[2].isNull()) {
         label = LabelFromValue(request.params[2]);
     }
 
     int required = request.params[0].get_int();
 
     // Get the public keys
     const UniValue &keys_or_addrs = request.params[1].get_array();
     std::vector<CPubKey> pubkeys;
     for (size_t i = 0; i < keys_or_addrs.size(); ++i) {
         if (IsHex(keys_or_addrs[i].get_str()) &&
             (keys_or_addrs[i].get_str().length() == 66 ||
              keys_or_addrs[i].get_str().length() == 130)) {
             pubkeys.push_back(HexToPubKey(keys_or_addrs[i].get_str()));
         } else {
             pubkeys.push_back(AddrToPubKey(config.GetChainParams(), pwallet,
                                            keys_or_addrs[i].get_str()));
         }
     }
 
     OutputType output_type = pwallet->m_default_address_type;
 
     // Construct using pay-to-script-hash:
     CScript inner = CreateMultisigRedeemscript(required, pubkeys);
     CTxDestination dest =
         AddAndGetDestinationForScript(*pwallet, inner, output_type);
     pwallet->SetAddressBook(dest, label, "send");
 
     UniValue result(UniValue::VOBJ);
     result.pushKV("address", EncodeDestination(dest, config));
     result.pushKV("redeemScript", HexStr(inner.begin(), inner.end()));
     return result;
 }
 
 struct tallyitem {
     Amount nAmount{Amount::zero()};
     int nConf{std::numeric_limits<int>::max()};
     std::vector<uint256> txids;
     bool fIsWatchonly{false};
     tallyitem() {}
 };
 
 static UniValue
 ListReceived(const Config &config, interfaces::Chain::Lock &locked_chain,
              CWallet *const pwallet, const UniValue &params, bool by_label)
     EXCLUSIVE_LOCKS_REQUIRED(pwallet->cs_wallet) {
     // Minimum confirmations
     int nMinDepth = 1;
     if (!params[0].isNull()) {
         nMinDepth = params[0].get_int();
     }
 
     // Whether to include empty labels
     bool fIncludeEmpty = false;
     if (!params[1].isNull()) {
         fIncludeEmpty = params[1].get_bool();
     }
 
     isminefilter filter = ISMINE_SPENDABLE;
     if (!params[2].isNull() && params[2].get_bool()) {
         filter = filter | ISMINE_WATCH_ONLY;
     }
 
     bool has_filtered_address = false;
     CTxDestination filtered_address = CNoDestination();
     if (!by_label && params.size() > 3) {
         if (!IsValidDestinationString(params[3].get_str(),
                                       config.GetChainParams())) {
             throw JSONRPCError(RPC_WALLET_ERROR,
                                "address_filter parameter was invalid");
         }
         filtered_address =
             DecodeDestination(params[3].get_str(), config.GetChainParams());
         has_filtered_address = true;
     }
 
     // Tally
     std::map<CTxDestination, tallyitem> mapTally;
     for (const std::pair<const TxId, CWalletTx> &pairWtx : pwallet->mapWallet) {
         const CWalletTx &wtx = pairWtx.second;
 
         CValidationState state;
         if (wtx.IsCoinBase() ||
             !locked_chain.contextualCheckTransactionForCurrentBlock(
                 config.GetChainParams().GetConsensus(), *wtx.tx, state)) {
             continue;
         }
 
         int nDepth = wtx.GetDepthInMainChain(locked_chain);
         if (nDepth < nMinDepth) {
             continue;
         }
 
         for (const CTxOut &txout : wtx.tx->vout) {
             CTxDestination address;
             if (!ExtractDestination(txout.scriptPubKey, address)) {
                 continue;
             }
 
             if (has_filtered_address && !(filtered_address == address)) {
                 continue;
             }
 
             isminefilter mine = IsMine(*pwallet, address);
             if (!(mine & filter)) {
                 continue;
             }
 
             tallyitem &item = mapTally[address];
             item.nAmount += txout.nValue;
             item.nConf = std::min(item.nConf, nDepth);
             item.txids.push_back(wtx.GetId());
             if (mine & ISMINE_WATCH_ONLY) {
                 item.fIsWatchonly = true;
             }
         }
     }
 
     // Reply
     UniValue ret(UniValue::VARR);
     std::map<std::string, tallyitem> label_tally;
 
     // Create mapAddressBook iterator
     // If we aren't filtering, go from begin() to end()
     auto start = pwallet->mapAddressBook.begin();
     auto end = pwallet->mapAddressBook.end();
     // If we are filtering, find() the applicable entry
     if (has_filtered_address) {
         start = pwallet->mapAddressBook.find(filtered_address);
         if (start != end) {
             end = std::next(start);
         }
     }
 
     for (auto item_it = start; item_it != end; ++item_it) {
         const CTxDestination &address = item_it->first;
         const std::string &label = item_it->second.name;
         std::map<CTxDestination, tallyitem>::iterator it =
             mapTally.find(address);
         if (it == mapTally.end() && !fIncludeEmpty) {
             continue;
         }
 
         Amount nAmount = Amount::zero();
         int nConf = std::numeric_limits<int>::max();
         bool fIsWatchonly = false;
         if (it != mapTally.end()) {
             nAmount = (*it).second.nAmount;
             nConf = (*it).second.nConf;
             fIsWatchonly = (*it).second.fIsWatchonly;
         }
 
         if (by_label) {
             tallyitem &_item = label_tally[label];
             _item.nAmount += nAmount;
             _item.nConf = std::min(_item.nConf, nConf);
             _item.fIsWatchonly = fIsWatchonly;
         } else {
             UniValue obj(UniValue::VOBJ);
             if (fIsWatchonly) {
                 obj.pushKV("involvesWatchonly", true);
             }
             obj.pushKV("address", EncodeDestination(address, config));
             obj.pushKV("amount", ValueFromAmount(nAmount));
             obj.pushKV("confirmations",
                        (nConf == std::numeric_limits<int>::max() ? 0 : nConf));
             obj.pushKV("label", label);
             UniValue transactions(UniValue::VARR);
             if (it != mapTally.end()) {
                 for (const uint256 &_item : (*it).second.txids) {
                     transactions.push_back(_item.GetHex());
                 }
             }
             obj.pushKV("txids", transactions);
             ret.push_back(obj);
         }
     }
 
     if (by_label) {
         for (const auto &entry : label_tally) {
             Amount nAmount = entry.second.nAmount;
             int nConf = entry.second.nConf;
             UniValue obj(UniValue::VOBJ);
             if (entry.second.fIsWatchonly) {
                 obj.pushKV("involvesWatchonly", true);
             }
             obj.pushKV("amount", ValueFromAmount(nAmount));
             obj.pushKV("confirmations",
                        (nConf == std::numeric_limits<int>::max() ? 0 : nConf));
             obj.pushKV("label", entry.first);
             ret.push_back(obj);
         }
     }
 
     return ret;
 }
 
 static UniValue listreceivedbyaddress(const Config &config,
                                       const JSONRPCRequest &request) {
     std::shared_ptr<CWallet> const wallet = GetWalletForJSONRPCRequest(request);
     CWallet *const pwallet = wallet.get();
 
     if (!EnsureWalletIsAvailable(pwallet, request.fHelp)) {
         return NullUniValue;
     }
 
     if (request.fHelp || request.params.size() > 4) {
         throw std::runtime_error(RPCHelpMan{
             "listreceivedbyaddress",
             "\nList balances by receiving address.\n",
             {
-                {"minconf", RPCArg::Type::NUM, /* opt */ true,
-                 /* default_val */ "1",
+                {"minconf", RPCArg::Type::NUM, /* default */ "1",
                  "The minimum number of confirmations before payments are "
                  "included."},
-                {"include_empty", RPCArg::Type::BOOL, /* opt */ true,
-                 /* default_val */ "false",
+                {"include_empty", RPCArg::Type::BOOL, /* default */ "false",
                  "Whether to include addresses that haven't received any "
                  "payments."},
-                {"include_watchonly", RPCArg::Type::BOOL, /* opt */ true,
-                 /* default_val */ "false",
+                {"include_watchonly", RPCArg::Type::BOOL, /* default */ "false",
                  "Whether to include watch-only addresses (see "
                  "'importaddress')."},
-                {"address_filter", RPCArg::Type::STR, /* opt */ true,
-                 /* default_val */ "null",
+                {"address_filter", RPCArg::Type::STR,
+                 RPCArg::Optional::OMITTED_NAMED_ARG,
                  "If present, only return information on this address."},
             },
             RPCResult{
                 "[\n"
                 "  {\n"
                 "    \"involvesWatchonly\" : true,        (bool) Only returned "
                 "if imported addresses were involved in transaction\n"
                 "    \"address\" : \"receivingaddress\",  (string) The "
                 "receiving address\n"
                 "    \"amount\" : x.xxx,                  (numeric) The total "
                 "amount in " +
                 CURRENCY_UNIT +
                 " received by the address\n"
                 "    \"confirmations\" : n,               (numeric) The number "
                 "of confirmations of the most recent transaction included\n"
                 "    \"label\" : \"label\",               (string) The label "
                 "of the receiving address. The default label is \"\".\n"
                 "    \"txids\": [\n"
                 "       \"txid\",                         (string) The ids of "
                 "transactions received with the address \n"
                 "       ...\n"
                 "    ]\n"
                 "  }\n"
                 "  ,...\n"
                 "]\n"},
             RPCExamples{
                 HelpExampleCli("listreceivedbyaddress", "") +
                 HelpExampleCli("listreceivedbyaddress", "6 true") +
                 HelpExampleRpc("listreceivedbyaddress", "6, true, true") +
                 HelpExampleRpc(
                     "listreceivedbyaddress",
                     "6, true, true, \"1M72Sfpbz1BPpXFHz9m3CdqATR44Jvaydd\"")},
         }
                                      .ToString());
     }
 
     // Make sure the results are valid at least up to the most recent block
     // the user could have gotten from another RPC command prior to now
     pwallet->BlockUntilSyncedToCurrentChain();
 
     auto locked_chain = pwallet->chain().lock();
     LOCK(pwallet->cs_wallet);
 
     return ListReceived(config, *locked_chain, pwallet, request.params, false);
 }
 
 static UniValue listreceivedbylabel(const Config &config,
                                     const JSONRPCRequest &request) {
     std::shared_ptr<CWallet> const wallet = GetWalletForJSONRPCRequest(request);
     CWallet *const pwallet = wallet.get();
 
     if (!EnsureWalletIsAvailable(pwallet, request.fHelp)) {
         return NullUniValue;
     }
 
     if (request.fHelp || request.params.size() > 3) {
         throw std::runtime_error(RPCHelpMan{
             "listreceivedbylabel",
             "\nList received transactions by label.\n",
             {
-                {"minconf", RPCArg::Type::NUM, /* opt */ true,
-                 /* default_val */ "1",
+                {"minconf", RPCArg::Type::NUM, /* default */ "1",
                  "The minimum number of confirmations before "
                  "payments are included."},
-                {"include_empty", RPCArg::Type::BOOL, /* opt */ true,
-                 /* default_val */ "false",
+                {"include_empty", RPCArg::Type::BOOL, /* default */ "false",
                  "Whether to include labels that haven't received "
                  "any payments."},
                 {"include_watchonly", RPCArg::Type::BOOL,
-                 /* opt */ true, /* default_val */ "false",
+                 /* default */ "false",
                  "Whether to include watch-only addresses (see "
                  "'importaddress')."},
             },
             RPCResult{
                 "[\n"
                 "  {\n"
                 "    \"involvesWatchonly\" : true,   (bool) Only returned if "
                 "imported addresses were involved in transaction\n"
                 "    \"amount\" : x.xxx,             (numeric) The total "
                 "amount received by addresses with this label\n"
                 "    \"confirmations\" : n,          (numeric) The number of "
                 "confirmations of the most recent transaction included\n"
                 "    \"label\" : \"label\"           (string) The label of the "
                 "receiving address. The default label is \"\".\n"
                 "  }\n"
                 "  ,...\n"
                 "]\n"},
             RPCExamples{HelpExampleCli("listreceivedbylabel", "") +
                         HelpExampleCli("listreceivedbylabel", "6 true") +
                         HelpExampleRpc("listreceivedbylabel", "6, true, true")},
         }
                                      .ToString());
     }
 
     // Make sure the results are valid at least up to the most recent block
     // the user could have gotten from another RPC command prior to now
     pwallet->BlockUntilSyncedToCurrentChain();
 
     auto locked_chain = pwallet->chain().lock();
     LOCK(pwallet->cs_wallet);
 
     return ListReceived(config, *locked_chain, pwallet, request.params, true);
 }
 
 static void MaybePushAddress(UniValue &entry, const CTxDestination &dest) {
     if (IsValidDestination(dest)) {
         entry.pushKV("address", EncodeDestination(dest, GetConfig()));
     }
 }
 
 /**
  * List transactions based on the given criteria.
  *
  * @param  pwallet        The wallet.
  * @param  wtx            The wallet transaction.
  * @param  nMinDepth      The minimum confirmation depth.
  * @param  fLong          Whether to include the JSON version of the
  * transaction.
  * @param  ret            The UniValue into which the result is stored.
  * @param  filter_ismine  The "is mine" filter flags.
  * @param  filter_label   Optional label string to filter incoming transactions.
  */
 static void ListTransactions(interfaces::Chain::Lock &locked_chain,
                              CWallet *const pwallet, const CWalletTx &wtx,
                              int nMinDepth, bool fLong, UniValue &ret,
                              const isminefilter &filter_ismine,
                              const std::string *filter_label) {
     Amount nFee;
     std::list<COutputEntry> listReceived;
     std::list<COutputEntry> listSent;
 
     wtx.GetAmounts(listReceived, listSent, nFee, filter_ismine);
 
     bool involvesWatchonly = wtx.IsFromMe(ISMINE_WATCH_ONLY);
 
     // Sent
     if (!filter_label) {
         for (const COutputEntry &s : listSent) {
             UniValue entry(UniValue::VOBJ);
             if (involvesWatchonly ||
                 (::IsMine(*pwallet, s.destination) & ISMINE_WATCH_ONLY)) {
                 entry.pushKV("involvesWatchonly", true);
             }
             MaybePushAddress(entry, s.destination);
             entry.pushKV("category", "send");
             entry.pushKV("amount", ValueFromAmount(-s.amount));
             if (pwallet->mapAddressBook.count(s.destination)) {
                 entry.pushKV("label",
                              pwallet->mapAddressBook[s.destination].name);
             }
             entry.pushKV("vout", s.vout);
             entry.pushKV("fee", ValueFromAmount(-1 * nFee));
             if (fLong) {
                 WalletTxToJSON(pwallet->chain(), locked_chain, wtx, entry);
             }
             entry.pushKV("abandoned", wtx.isAbandoned());
             ret.push_back(entry);
         }
     }
 
     // Received
     if (listReceived.size() > 0 &&
         wtx.GetDepthInMainChain(locked_chain) >= nMinDepth) {
         for (const COutputEntry &r : listReceived) {
             std::string label;
             if (pwallet->mapAddressBook.count(r.destination)) {
                 label = pwallet->mapAddressBook[r.destination].name;
             }
             if (filter_label && label != *filter_label) {
                 continue;
             }
             UniValue entry(UniValue::VOBJ);
             if (involvesWatchonly ||
                 (::IsMine(*pwallet, r.destination) & ISMINE_WATCH_ONLY)) {
                 entry.pushKV("involvesWatchonly", true);
             }
             MaybePushAddress(entry, r.destination);
             if (wtx.IsCoinBase()) {
                 if (wtx.GetDepthInMainChain(locked_chain) < 1) {
                     entry.pushKV("category", "orphan");
                 } else if (wtx.IsImmatureCoinBase(locked_chain)) {
                     entry.pushKV("category", "immature");
                 } else {
                     entry.pushKV("category", "generate");
                 }
             } else {
                 entry.pushKV("category", "receive");
             }
             entry.pushKV("amount", ValueFromAmount(r.amount));
             if (pwallet->mapAddressBook.count(r.destination)) {
                 entry.pushKV("label", label);
             }
             entry.pushKV("vout", r.vout);
             if (fLong) {
                 WalletTxToJSON(pwallet->chain(), locked_chain, wtx, entry);
             }
             ret.push_back(entry);
         }
     }
 }
 
 UniValue listtransactions(const Config &config, const JSONRPCRequest &request) {
     std::shared_ptr<CWallet> const wallet = GetWalletForJSONRPCRequest(request);
     CWallet *const pwallet = wallet.get();
 
     if (!EnsureWalletIsAvailable(pwallet, request.fHelp)) {
         return NullUniValue;
     }
 
     if (request.fHelp || request.params.size() > 4) {
         throw std::runtime_error(RPCHelpMan{
             "listtransactions",
             "\nIf a label name is provided, this will return only incoming "
             "transactions paying to addresses with the specified label.\n"
             "\nReturns up to 'count' most recent transactions skipping the "
             "first 'from' transactions.\n",
             {
-                {"label", RPCArg::Type::STR, /* opt */ true,
-                 /* default_val */ "null",
+                {"label", RPCArg::Type::STR,
+                 RPCArg::Optional::OMITTED_NAMED_ARG,
                  "If set, should be a valid label name to return only incoming "
                  "transactions with the specified label, or \"*\" to disable "
                  "filtering and return all transactions."},
-                {"count", RPCArg::Type::NUM, /* opt */ true,
-                 /* default_val */ "10",
+                {"count", RPCArg::Type::NUM, /* default */ "10",
                  "The number of transactions to return"},
-                {"skip", RPCArg::Type::NUM, /* opt */ true,
-                 /* default_val */ "0", "The number of transactions to skip"},
-                {"include_watchonly", RPCArg::Type::BOOL, /* opt */ true,
-                 /* default_val */ "false",
+                {"skip", RPCArg::Type::NUM, /* default */ "0",
+                 "The number of transactions to skip"},
+                {"include_watchonly", RPCArg::Type::BOOL, /* default */ "false",
                  "Include transactions to watch-only addresses (see "
                  "'importaddress')"},
             },
             RPCResult{
                 "[\n"
                 "  {\n"
                 "    \"address\":\"address\",    (string) The bitcoin address "
                 "of the transaction.\n"
                 "    \"category\":\"send|receive\", (string) The transaction "
                 "category.\n"
                 "    \"amount\": x.xxx,          (numeric) The amount in " +
                 CURRENCY_UNIT +
                 ". This is negative for the 'send' category, and is positive\n"
                 "                                        for the 'receive' "
                 "category,\n"
                 "    \"label\": \"label\",       (string) A comment for the "
                 "address/transaction, if any\n"
                 "    \"vout\": n,                (numeric) the vout value\n"
                 "    \"fee\": x.xxx,             (numeric) The amount of the "
                 "fee in " +
                 CURRENCY_UNIT +
                 ". This is negative and only available for the \n"
                 "                                         'send' category of "
                 "transactions.\n"
                 "    \"confirmations\": n,       (numeric) The number of "
                 "confirmations for the transaction. Negative confirmations "
                 "indicate the\n"
                 "                                         transaction "
                 "conflicts with the block chain\n"
                 "    \"trusted\": xxx,           (bool) Whether we consider "
                 "the outputs of this unconfirmed transaction safe to spend.\n"
                 "    \"blockhash\": \"hashvalue\", (string) The block hash "
                 "containing the transaction.\n"
                 "    \"blockindex\": n,          (numeric) The index of the "
                 "transaction in the block that includes it.\n"
                 "    \"blocktime\": xxx,         (numeric) The block time in "
                 "seconds since epoch (1 Jan 1970 GMT).\n"
                 "    \"txid\": \"transactionid\", (string) The transaction "
                 "id.\n"
                 "    \"time\": xxx,              (numeric) The transaction "
                 "time in seconds since epoch (midnight Jan 1 1970 GMT).\n"
                 "    \"timereceived\": xxx,      (numeric) The time received "
                 "in seconds since epoch (midnight Jan 1 1970 GMT).\n"
                 "    \"comment\": \"...\",       (string) If a comment is "
                 "associated with the transaction.\n"
                 "    \"abandoned\": xxx          (bool) 'true' if the "
                 "transaction has been abandoned (inputs are respendable). Only "
                 "available for the \n"
                 "                                         'send' category of "
                 "transactions.\n"
                 "  }\n"
                 "]\n"},
             RPCExamples{
                 "\nList the most recent 10 transactions in the systems\n" +
                 HelpExampleCli("listtransactions", "") +
                 "\nList transactions 100 to 120\n" +
                 HelpExampleCli("listtransactions", "\"*\" 20 100") +
                 "\nAs a JSON-RPC call\n" +
                 HelpExampleRpc("listtransactions", "\"*\", 20, 100")},
         }
                                      .ToString());
     }
 
     // Make sure the results are valid at least up to the most recent block
     // the user could have gotten from another RPC command prior to now
     pwallet->BlockUntilSyncedToCurrentChain();
 
     auto locked_chain = pwallet->chain().lock();
     LOCK(pwallet->cs_wallet);
 
     const std::string *filter_label = nullptr;
     if (!request.params[0].isNull() && request.params[0].get_str() != "*") {
         filter_label = &request.params[0].get_str();
         if (filter_label->empty()) {
             throw JSONRPCError(
                 RPC_INVALID_PARAMETER,
                 "Label argument must be a valid label name or \"*\".");
         }
     }
     int nCount = 10;
     if (!request.params[1].isNull()) {
         nCount = request.params[1].get_int();
     }
 
     int nFrom = 0;
     if (!request.params[2].isNull()) {
         nFrom = request.params[2].get_int();
     }
 
     isminefilter filter = ISMINE_SPENDABLE;
     if (!request.params[3].isNull() && request.params[3].get_bool()) {
         filter = filter | ISMINE_WATCH_ONLY;
     }
 
     if (nCount < 0) {
         throw JSONRPCError(RPC_INVALID_PARAMETER, "Negative count");
     }
     if (nFrom < 0) {
         throw JSONRPCError(RPC_INVALID_PARAMETER, "Negative from");
     }
     UniValue ret(UniValue::VARR);
 
     const CWallet::TxItems &txOrdered = pwallet->wtxOrdered;
 
     // iterate backwards until we have nCount items to return:
     for (CWallet::TxItems::const_reverse_iterator it = txOrdered.rbegin();
          it != txOrdered.rend(); ++it) {
         CWalletTx *const pwtx = (*it).second;
         ListTransactions(*locked_chain, pwallet, *pwtx, 0, true, ret, filter,
                          filter_label);
         if ((int)ret.size() >= (nCount + nFrom)) {
             break;
         }
     }
 
     // ret is newest to oldest
 
     if (nFrom > (int)ret.size()) {
         nFrom = ret.size();
     }
     if ((nFrom + nCount) > (int)ret.size()) {
         nCount = ret.size() - nFrom;
     }
 
     std::vector<UniValue> arrTmp = ret.getValues();
 
     std::vector<UniValue>::iterator first = arrTmp.begin();
     std::advance(first, nFrom);
     std::vector<UniValue>::iterator last = arrTmp.begin();
     std::advance(last, nFrom + nCount);
 
     if (last != arrTmp.end()) {
         arrTmp.erase(last, arrTmp.end());
     }
     if (first != arrTmp.begin()) {
         arrTmp.erase(arrTmp.begin(), first);
     }
 
     // Return oldest to newest
     std::reverse(arrTmp.begin(), arrTmp.end());
 
     ret.clear();
     ret.setArray();
     ret.push_backV(arrTmp);
 
     return ret;
 }
 
 static UniValue listsinceblock(const Config &config,
                                const JSONRPCRequest &request) {
     std::shared_ptr<CWallet> const wallet = GetWalletForJSONRPCRequest(request);
     CWallet *const pwallet = wallet.get();
 
     if (!EnsureWalletIsAvailable(pwallet, request.fHelp)) {
         return NullUniValue;
     }
 
     if (request.fHelp || request.params.size() > 4) {
         throw std::runtime_error(RPCHelpMan{
             "listsinceblock",
             "\nGet all transactions in blocks since block [blockhash], or all "
             "transactions if omitted.\n"
             "If \"blockhash\" is no longer a part of the main chain, "
             "transactions from the fork point onward are included.\n"
             "Additionally, if include_removed is set, transactions affecting "
             "the wallet which were removed are returned in the \"removed\" "
             "array.\n",
             {
-                {"blockhash", RPCArg::Type::STR, /* opt */ true,
-                 /* default_val */ "null",
+                {"blockhash", RPCArg::Type::STR,
+                 RPCArg::Optional::OMITTED_NAMED_ARG,
                  "If set, the block hash to list transactions since, otherwise "
                  "list all transactions."},
-                {"target_confirmations", RPCArg::Type::NUM, /* opt */ true,
-                 /* default_val */ "1",
+                {"target_confirmations", RPCArg::Type::NUM, /* default */ "1",
                  "Return the nth block hash from the main chain. e.g. 1 "
                  "would mean the best block hash. Note: this is not used "
                  "as a filter, but only affects [lastblock] in the return "
                  "value"},
-                {"include_watchonly", RPCArg::Type::BOOL, /* opt */ true,
-                 /* default_val */ "false",
+                {"include_watchonly", RPCArg::Type::BOOL, /* default */ "false",
                  "Include transactions to watch-only addresses (see "
                  "'importaddress')"},
-                {"include_removed", RPCArg::Type::BOOL, /* opt */ true,
-                 /* default_val */ "true",
+                {"include_removed", RPCArg::Type::BOOL, /* default */ "true",
                  "Show transactions that were removed due to a reorg in "
                  "the \"removed\" array\n"
                  "                                                         "
                  "  (not guaranteed to work on pruned nodes)"},
             },
             RPCResult{
                 "{\n"
                 "  \"transactions\": [\n"
                 "    \"address\":\"address\",    (string) The bitcoin address "
                 "of the transaction. Not present for move transactions "
                 "(category = move).\n"
                 "    \"category\":\"send|receive\",     (string) The "
                 "transaction category. 'send' has negative amounts, 'receive' "
                 "has positive amounts.\n"
                 "    \"amount\": x.xxx,          (numeric) The amount in " +
                 CURRENCY_UNIT +
                 ". This is negative for the 'send' category, and for the "
                 "'move' category for moves \n"
                 "                                          outbound. It is "
                 "positive for the 'receive' category, and for the 'move' "
                 "category for inbound funds.\n"
                 "    \"vout\" : n,               (numeric) the vout value\n"
                 "    \"fee\": x.xxx,             (numeric) The amount of the "
                 "fee in " +
                 CURRENCY_UNIT +
                 ". This is negative and only available for the 'send' category "
                 "of transactions.\n"
                 "    \"confirmations\": n,       (numeric) The number of "
                 "confirmations for the transaction. Available for 'send' and "
                 "'receive' category of transactions.\n"
                 "                                          When it's < 0, it "
                 "means the transaction conflicted that many blocks ago.\n"
                 "    \"blockhash\": \"hashvalue\",     (string) The block hash "
                 "containing the transaction. Available for 'send' and "
                 "'receive' category of transactions.\n"
                 "    \"blockindex\": n,          (numeric) The index of the "
                 "transaction in the block that includes it. Available for "
                 "'send' and 'receive' category of transactions.\n"
                 "    \"blocktime\": xxx,         (numeric) The block time in "
                 "seconds since epoch (1 Jan 1970 GMT).\n"
                 "    \"txid\": \"transactionid\",  (string) The transaction "
                 "id. Available for 'send' and 'receive' category of "
                 "transactions.\n"
                 "    \"time\": xxx,              (numeric) The transaction "
                 "time in seconds since epoch (Jan 1 1970 GMT).\n"
                 "    \"timereceived\": xxx,      (numeric) The time received "
                 "in seconds since epoch (Jan 1 1970 GMT). Available for 'send' "
                 "and 'receive' category of transactions.\n"
                 "    \"abandoned\": xxx,         (bool) 'true' if the "
                 "transaction has been abandoned (inputs are respendable). Only "
                 "available for the 'send' category of transactions.\n"
                 "    \"comment\": \"...\",       (string) If a comment is "
                 "associated with the transaction.\n"
                 "    \"label\" : \"label\"       (string) A comment for the "
                 "address/transaction, if any\n"
                 "    \"to\": \"...\",            (string) If a comment to is "
                 "associated with the transaction.\n"
                 "  ],\n"
                 "  \"removed\": [\n"
                 "    <structure is the same as \"transactions\" above, only "
                 "present if include_removed=true>\n"
                 "    Note: transactions that were re-added in the active chain "
                 "will appear as-is in this array, and may thus have a positive "
                 "confirmation count.\n"
                 "  ],\n"
                 "  \"lastblock\": \"lastblockhash\"     (string) The hash of "
                 "the block (target_confirmations-1) from the best block on the "
                 "main chain. This is typically used to feed back into "
                 "listsinceblock the next time you call it. So you would "
                 "generally use a target_confirmations of say 6, so you will be "
                 "continually re-notified of transactions until they've reached "
                 "6 confirmations plus any new ones\n"
                 "}\n"},
             RPCExamples{HelpExampleCli("listsinceblock", "") +
                         HelpExampleCli("listsinceblock",
                                        "\"000000000000000bacf66f7497b7dc4"
                                        "5ef753ee9a7d38571037cdb1a57f663ad"
                                        "\" 6") +
                         HelpExampleRpc("listsinceblock",
                                        "\"000000000000000bacf66f7497b7dc4"
                                        "5ef753ee9a7d38571037cdb1a57f663ad"
                                        "\", 6")},
         }
                                      .ToString());
     }
 
     // Make sure the results are valid at least up to the most recent block
     // the user could have gotten from another RPC command prior to now
     pwallet->BlockUntilSyncedToCurrentChain();
 
     auto locked_chain = pwallet->chain().lock();
     LOCK(pwallet->cs_wallet);
 
     // The way the 'height' is initialized is just a workaround for the gcc bug
     // #47679 since version 4.6.0. Height of the specified block or the common
     // ancestor, if the block provided was in a deactivated chain.
     Optional<int> height = MakeOptional(false, int());
 
     // Height of the specified block, even if it's in a deactivated chain.
     Optional<int> altheight;
     int target_confirms = 1;
     isminefilter filter = ISMINE_SPENDABLE;
 
     BlockHash blockId;
     if (!request.params[0].isNull() && !request.params[0].get_str().empty()) {
         blockId = BlockHash(ParseHashV(request.params[0], "blockhash"));
         height = locked_chain->findFork(blockId, &altheight);
         if (!height) {
             throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Block not found");
         }
     }
 
     if (!request.params[1].isNull()) {
         target_confirms = request.params[1].get_int();
 
         if (target_confirms < 1) {
             throw JSONRPCError(RPC_INVALID_PARAMETER, "Invalid parameter");
         }
     }
 
     if (!request.params[2].isNull() && request.params[2].get_bool()) {
         filter = filter | ISMINE_WATCH_ONLY;
     }
 
     bool include_removed =
         (request.params[3].isNull() || request.params[3].get_bool());
 
     const Optional<int> tip_height = locked_chain->getHeight();
     int depth = tip_height && height ? (1 + *tip_height - *height) : -1;
 
     UniValue transactions(UniValue::VARR);
 
     for (const std::pair<const TxId, CWalletTx> &pairWtx : pwallet->mapWallet) {
         CWalletTx tx = pairWtx.second;
 
         if (depth == -1 || tx.GetDepthInMainChain(*locked_chain) < depth) {
             ListTransactions(*locked_chain, pwallet, tx, 0, true, transactions,
                              filter, nullptr /* filter_label */);
         }
     }
 
     // when a reorg'd block is requested, we also list any relevant transactions
     // in the blocks of the chain that was detached
     UniValue removed(UniValue::VARR);
     while (include_removed && altheight && *altheight > *height) {
         CBlock block;
         if (!pwallet->chain().findBlock(blockId, &block) || block.IsNull()) {
             throw JSONRPCError(RPC_INTERNAL_ERROR,
                                "Can't read block from disk");
         }
         for (const CTransactionRef &tx : block.vtx) {
             auto it = pwallet->mapWallet.find(tx->GetId());
             if (it != pwallet->mapWallet.end()) {
                 // We want all transactions regardless of confirmation count to
                 // appear here, even negative confirmation ones, hence the big
                 // negative.
                 ListTransactions(*locked_chain, pwallet, it->second, -100000000,
                                  true, removed, filter,
                                  nullptr /* filter_label */);
             }
         }
         blockId = block.hashPrevBlock;
         --*altheight;
     }
 
     int last_height = tip_height ? *tip_height + 1 - target_confirms : -1;
     BlockHash lastblock = last_height >= 0
                               ? locked_chain->getBlockHash(last_height)
                               : BlockHash();
 
     UniValue ret(UniValue::VOBJ);
     ret.pushKV("transactions", transactions);
     if (include_removed) {
         ret.pushKV("removed", removed);
     }
     ret.pushKV("lastblock", lastblock.GetHex());
 
     return ret;
 }
 
 static UniValue gettransaction(const Config &config,
                                const JSONRPCRequest &request) {
     std::shared_ptr<CWallet> const wallet = GetWalletForJSONRPCRequest(request);
     CWallet *const pwallet = wallet.get();
 
     if (!EnsureWalletIsAvailable(pwallet, request.fHelp)) {
         return NullUniValue;
     }
 
     if (request.fHelp || request.params.size() < 1 ||
         request.params.size() > 2) {
         throw std::runtime_error(RPCHelpMan{
             "gettransaction",
             "\nGet detailed information about in-wallet transaction "
             "<txid>\n",
             {
-                {"txid", RPCArg::Type::STR, /* opt */ false,
-                 /* default_val */ "", "The transaction id"},
+                {"txid", RPCArg::Type::STR, RPCArg::Optional::NO,
+                 "The transaction id"},
                 {"include_watchonly", RPCArg::Type::BOOL,
-                 /* opt */ true, /* default_val */ "false",
+                 /* default */ "false",
                  "Whether to include watch-only addresses in "
                  "balance calculation and details[]"},
             },
             RPCResult{
                 "{\n"
                 "  \"amount\" : x.xxx,        (numeric) The transaction amount "
                 "in " +
                 CURRENCY_UNIT +
                 "\n"
                 "  \"fee\": x.xxx,            (numeric) The amount of the fee "
                 "in " +
                 CURRENCY_UNIT +
                 ". This is negative and only available for the \n"
                 "                              'send' category of "
                 "transactions.\n"
                 "  \"confirmations\" : n,     (numeric) The number of "
                 "confirmations\n"
                 "  \"blockhash\" : \"hash\",  (string) The block hash\n"
                 "  \"blockindex\" : xx,       (numeric) The index of the "
                 "transaction in the block that includes it\n"
                 "  \"blocktime\" : ttt,       (numeric) The time in seconds "
                 "since epoch (1 Jan 1970 GMT)\n"
                 "  \"txid\" : \"transactionid\",   (string) The transaction "
                 "id.\n"
                 "  \"time\" : ttt,            (numeric) The transaction time "
                 "in seconds since epoch (1 Jan 1970 GMT)\n"
                 "  \"timereceived\" : ttt,    (numeric) The time received in "
                 "seconds since epoch (1 Jan 1970 GMT)\n"
                 "  \"bip125-replaceable\": \"yes|no|unknown\",  (string) "
                 "Whether this transaction could be replaced due to BIP125 "
                 "(replace-by-fee);\n"
                 "                                                   may be "
                 "unknown for unconfirmed transactions not in the mempool\n"
                 "  \"details\" : [\n"
                 "    {\n"
                 "      \"address\" : \"address\",          (string) The "
                 "bitcoin address involved in the transaction\n"
                 "      \"category\" : \"send|receive\",    (string) The "
                 "category, either 'send' or 'receive'\n"
                 "      \"amount\" : x.xxx,                 (numeric) The "
                 "amount in " +
                 CURRENCY_UNIT +
                 "\n"
                 "      \"label\" : \"label\",              (string) A comment "
                 "for the address/transaction, if any\n"
                 "      \"vout\" : n,                       (numeric) the vout "
                 "value\n"
                 "      \"fee\": x.xxx,                     (numeric) The "
                 "amount of the fee in " +
                 CURRENCY_UNIT +
                 ". This is negative and only available for the \n"
                 "                                           'send' category of "
                 "transactions.\n"
                 "      \"abandoned\": xxx                  (bool) 'true' if "
                 "the transaction has been abandoned (inputs are respendable). "
                 "Only available for the \n"
                 "                                           'send' category of "
                 "transactions.\n"
                 "    }\n"
                 "    ,...\n"
                 "  ],\n"
                 "  \"hex\" : \"data\"         (string) Raw data for "
                 "transaction\n"
                 "}\n"},
             RPCExamples{HelpExampleCli("gettransaction",
                                        "\"1075db55d416d3ca199f55b6084e211"
                                        "5b9345e16c5cf302fc80e9d5fbf5d48d"
                                        "\"") +
                         HelpExampleCli("gettransaction",
                                        "\"1075db55d416d3ca199f55b6084e211"
                                        "5b9345e16c5cf302fc80e9d5fbf5d48d"
                                        "\" true") +
                         HelpExampleRpc("gettransaction",
                                        "\"1075db55d416d3ca199f55b6084e211"
                                        "5b9345e16c5cf302fc80e9d5fbf5d48d"
                                        "\"")},
         }
                                      .ToString());
     }
 
     // Make sure the results are valid at least up to the most recent block
     // the user could have gotten from another RPC command prior to now
     pwallet->BlockUntilSyncedToCurrentChain();
 
     auto locked_chain = pwallet->chain().lock();
     LOCK(pwallet->cs_wallet);
 
     TxId txid(ParseHashV(request.params[0], "txid"));
 
     isminefilter filter = ISMINE_SPENDABLE;
     if (!request.params[1].isNull() && request.params[1].get_bool()) {
         filter = filter | ISMINE_WATCH_ONLY;
     }
 
     UniValue entry(UniValue::VOBJ);
     auto it = pwallet->mapWallet.find(txid);
     if (it == pwallet->mapWallet.end()) {
         throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY,
                            "Invalid or non-wallet transaction id");
     }
     const CWalletTx &wtx = it->second;
 
     Amount nCredit = wtx.GetCredit(*locked_chain, filter);
     Amount nDebit = wtx.GetDebit(filter);
     Amount nNet = nCredit - nDebit;
     Amount nFee = (wtx.IsFromMe(filter) ? wtx.tx->GetValueOut() - nDebit
                                         : Amount::zero());
 
     entry.pushKV("amount", ValueFromAmount(nNet - nFee));
     if (wtx.IsFromMe(filter)) {
         entry.pushKV("fee", ValueFromAmount(nFee));
     }
 
     WalletTxToJSON(pwallet->chain(), *locked_chain, wtx, entry);
 
     UniValue details(UniValue::VARR);
     ListTransactions(*locked_chain, pwallet, wtx, 0, false, details, filter,
                      nullptr /* filter_label */);
     entry.pushKV("details", details);
 
     std::string strHex = EncodeHexTx(*wtx.tx, RPCSerializationFlags());
     entry.pushKV("hex", strHex);
 
     return entry;
 }
 
 static UniValue abandontransaction(const Config &config,
                                    const JSONRPCRequest &request) {
     std::shared_ptr<CWallet> const wallet = GetWalletForJSONRPCRequest(request);
     CWallet *const pwallet = wallet.get();
 
     if (!EnsureWalletIsAvailable(pwallet, request.fHelp)) {
         return NullUniValue;
     }
 
     if (request.fHelp || request.params.size() != 1) {
         throw std::runtime_error(RPCHelpMan{
             "abandontransaction",
             "\nMark in-wallet transaction <txid> as abandoned\n"
             "This will mark this transaction and all its in-wallet descendants "
             "as abandoned which will allow\n"
             "for their inputs to be respent.  It can be used to replace "
             "\"stuck\" or evicted transactions.\n"
             "It only works on transactions which are not included in a block "
             "and are not currently in the mempool.\n"
             "It has no effect on transactions which are already abandoned.\n",
             {
-                {"txid", RPCArg::Type::STR_HEX, /* opt */ false,
-                 /* default_val */ "", "The transaction id"},
+                {"txid", RPCArg::Type::STR_HEX, RPCArg::Optional::NO,
+                 "The transaction id"},
             },
             RPCResults{},
             RPCExamples{HelpExampleCli("abandontransaction",
                                        "\"1075db55d416d3ca199f55b6084"
                                        "e2115b9345e16c5cf302fc80e9d5f"
                                        "bf5d48d\"") +
                         HelpExampleRpc("abandontransaction",
                                        "\"1075db55d416d3ca199f55b6084"
                                        "e2115b9345e16c5cf302fc80e9d5f"
                                        "bf5d48d\"")},
         }
                                      .ToString());
     }
 
     // Make sure the results are valid at least up to the most recent block
     // the user could have gotten from another RPC command prior to now
     pwallet->BlockUntilSyncedToCurrentChain();
 
     auto locked_chain = pwallet->chain().lock();
     LOCK(pwallet->cs_wallet);
 
     TxId txid(ParseHashV(request.params[0], "txid"));
 
     if (!pwallet->mapWallet.count(txid)) {
         throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY,
                            "Invalid or non-wallet transaction id");
     }
 
     if (!pwallet->AbandonTransaction(*locked_chain, txid)) {
         throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY,
                            "Transaction not eligible for abandonment");
     }
 
     return NullUniValue;
 }
 
 static UniValue backupwallet(const Config &config,
                              const JSONRPCRequest &request) {
     std::shared_ptr<CWallet> const wallet = GetWalletForJSONRPCRequest(request);
     CWallet *const pwallet = wallet.get();
 
     if (!EnsureWalletIsAvailable(pwallet, request.fHelp)) {
         return NullUniValue;
     }
 
     if (request.fHelp || request.params.size() != 1) {
         throw std::runtime_error(RPCHelpMan{
             "backupwallet",
             "\nSafely copies current wallet file to destination, "
             "which can be a directory or a path with filename.\n",
             {
-                {"destination", RPCArg::Type::STR, /* opt */ false,
-                 /* default_val */ "", "The destination directory or file"},
+                {"destination", RPCArg::Type::STR, RPCArg::Optional::NO,
+                 "The destination directory or file"},
             },
             RPCResults{},
             RPCExamples{HelpExampleCli("backupwallet", "\"backup.dat\"") +
                         HelpExampleRpc("backupwallet", "\"backup.dat\"")},
         }
                                      .ToString());
     }
 
     // Make sure the results are valid at least up to the most recent block
     // the user could have gotten from another RPC command prior to now
     pwallet->BlockUntilSyncedToCurrentChain();
 
     auto locked_chain = pwallet->chain().lock();
     LOCK(pwallet->cs_wallet);
 
     std::string strDest = request.params[0].get_str();
     if (!pwallet->BackupWallet(strDest)) {
         throw JSONRPCError(RPC_WALLET_ERROR, "Error: Wallet backup failed!");
     }
 
     return NullUniValue;
 }
 
 static UniValue keypoolrefill(const Config &config,
                               const JSONRPCRequest &request) {
     std::shared_ptr<CWallet> const wallet = GetWalletForJSONRPCRequest(request);
     CWallet *const pwallet = wallet.get();
 
     if (!EnsureWalletIsAvailable(pwallet, request.fHelp)) {
         return NullUniValue;
     }
 
     if (request.fHelp || request.params.size() > 1) {
         throw std::runtime_error(RPCHelpMan{
             "keypoolrefill",
             "\nFills the keypool." + HelpRequiringPassphrase(pwallet) + "\n",
             {
-                {"newsize", RPCArg::Type::NUM, /* opt */ true,
-                 /* default_val */ "100", "The new keypool size"},
+                {"newsize", RPCArg::Type::NUM, /* default */ "100",
+                 "The new keypool size"},
             },
             RPCResults{},
             RPCExamples{HelpExampleCli("keypoolrefill", "") +
                         HelpExampleRpc("keypoolrefill", "")},
         }
                                      .ToString());
     }
 
     if (pwallet->IsWalletFlagSet(WALLET_FLAG_DISABLE_PRIVATE_KEYS)) {
         throw JSONRPCError(RPC_WALLET_ERROR,
                            "Error: Private keys are disabled for this wallet");
     }
 
     auto locked_chain = pwallet->chain().lock();
     LOCK(pwallet->cs_wallet);
 
     // 0 is interpreted by TopUpKeyPool() as the default keypool size given by
     // -keypool
     unsigned int kpSize = 0;
     if (!request.params[0].isNull()) {
         if (request.params[0].get_int() < 0) {
             throw JSONRPCError(RPC_INVALID_PARAMETER,
                                "Invalid parameter, expected valid size.");
         }
         kpSize = (unsigned int)request.params[0].get_int();
     }
 
     EnsureWalletIsUnlocked(pwallet);
     pwallet->TopUpKeyPool(kpSize);
 
     if (pwallet->GetKeyPoolSize() < kpSize) {
         throw JSONRPCError(RPC_WALLET_ERROR, "Error refreshing keypool.");
     }
 
     return NullUniValue;
 }
 
 static void LockWallet(CWallet *pWallet) {
     LOCK(pWallet->cs_wallet);
     pWallet->nRelockTime = 0;
     pWallet->Lock();
 }
 
 static UniValue walletpassphrase(const Config &config,
                                  const JSONRPCRequest &request) {
     std::shared_ptr<CWallet> const wallet = GetWalletForJSONRPCRequest(request);
     CWallet *const pwallet = wallet.get();
 
     if (!EnsureWalletIsAvailable(pwallet, request.fHelp)) {
         return NullUniValue;
     }
 
     if (pwallet->IsCrypted() && (request.fHelp || request.params.size() != 2)) {
         throw std::runtime_error(RPCHelpMan{
             "walletpassphrase",
             "\nStores the wallet decryption key in memory for 'timeout' "
             "seconds.\n"
             "This is needed prior to performing transactions related to "
             "private keys such as sending bitcoins\n"
             "\nNote:\n"
             "Issuing the walletpassphrase command while the wallet is already "
             "unlocked will set a new unlock\n"
             "time that overrides the old one.\n",
             {
-                {"passphrase", RPCArg::Type::STR, /* opt */ false,
-                 /* default_val */ "", "The wallet passphrase"},
-                {"timeout", RPCArg::Type::NUM, /* opt */ false,
-                 /* default_val */ "",
+                {"passphrase", RPCArg::Type::STR, RPCArg::Optional::NO,
+                 "The wallet passphrase"},
+                {"timeout", RPCArg::Type::NUM, RPCArg::Optional::NO,
                  "The time to keep the decryption key in seconds; capped "
                  "at 100000000 (~3 years)."},
             },
             RPCResults{},
             RPCExamples{
                 "\nUnlock the wallet for 60 seconds\n" +
                 HelpExampleCli("walletpassphrase", "\"my pass phrase\" 60") +
                 "\nLock the wallet again (before 60 seconds)\n" +
                 HelpExampleCli("walletlock", "") + "\nAs a JSON-RPC call\n" +
                 HelpExampleRpc("walletpassphrase", "\"my pass phrase\", 60")},
         }
                                      .ToString());
     }
 
     auto locked_chain = pwallet->chain().lock();
     LOCK(pwallet->cs_wallet);
 
     if (request.fHelp) {
         return true;
     }
 
     if (!pwallet->IsCrypted()) {
         throw JSONRPCError(RPC_WALLET_WRONG_ENC_STATE,
                            "Error: running with an unencrypted wallet, but "
                            "walletpassphrase was called.");
     }
 
     // Note that the walletpassphrase is stored in request.params[0] which is
     // not mlock()ed
     SecureString strWalletPass;
     strWalletPass.reserve(100);
     // TODO: get rid of this .c_str() by implementing
     // SecureString::operator=(std::string)
     // Alternately, find a way to make request.params[0] mlock()'d to begin
     // with.
     strWalletPass = request.params[0].get_str().c_str();
 
     // Get the timeout
     int64_t nSleepTime = request.params[1].get_int64();
     // Timeout cannot be negative, otherwise it will relock immediately
     if (nSleepTime < 0) {
         throw JSONRPCError(RPC_INVALID_PARAMETER,
                            "Timeout cannot be negative.");
     }
     // Clamp timeout
     // larger values trigger a macos/libevent bug?
     constexpr int64_t MAX_SLEEP_TIME = 100000000;
     if (nSleepTime > MAX_SLEEP_TIME) {
         nSleepTime = MAX_SLEEP_TIME;
     }
 
     if (strWalletPass.empty()) {
         throw JSONRPCError(RPC_INVALID_PARAMETER,
                            "passphrase can not be empty");
     }
 
     if (!pwallet->Unlock(strWalletPass)) {
         throw JSONRPCError(
             RPC_WALLET_PASSPHRASE_INCORRECT,
             "Error: The wallet passphrase entered was incorrect.");
     }
 
     pwallet->TopUpKeyPool();
 
     pwallet->nRelockTime = GetTime() + nSleepTime;
     RPCRunLater(strprintf("lockwallet(%s)", pwallet->GetName()),
                 std::bind(LockWallet, pwallet), nSleepTime);
 
     return NullUniValue;
 }
 
 static UniValue walletpassphrasechange(const Config &config,
                                        const JSONRPCRequest &request) {
     std::shared_ptr<CWallet> const wallet = GetWalletForJSONRPCRequest(request);
     CWallet *const pwallet = wallet.get();
 
     if (!EnsureWalletIsAvailable(pwallet, request.fHelp)) {
         return NullUniValue;
     }
 
     if (pwallet->IsCrypted() && (request.fHelp || request.params.size() != 2)) {
         throw std::runtime_error(RPCHelpMan{
             "walletpassphrasechange",
             "\nChanges the wallet passphrase from 'oldpassphrase' to "
             "'newpassphrase'.\n",
             {
-                {"oldpassphrase", RPCArg::Type::STR, /* opt */ false,
-                 /* default_val */ "", "The current passphrase"},
-                {"newpassphrase", RPCArg::Type::STR, /* opt */ false,
-                 /* default_val */ "", "The new passphrase"},
+                {"oldpassphrase", RPCArg::Type::STR, RPCArg::Optional::NO,
+                 "The current passphrase"},
+                {"newpassphrase", RPCArg::Type::STR, RPCArg::Optional::NO,
+                 "The new passphrase"},
             },
             RPCResults{},
             RPCExamples{HelpExampleCli("walletpassphrasechange",
                                        "\"old one\" \"new one\"") +
                         HelpExampleRpc("walletpassphrasechange",
                                        "\"old one\", \"new one\"")},
         }
                                      .ToString());
     }
 
     auto locked_chain = pwallet->chain().lock();
     LOCK(pwallet->cs_wallet);
 
     if (request.fHelp) {
         return true;
     }
     if (!pwallet->IsCrypted()) {
         throw JSONRPCError(RPC_WALLET_WRONG_ENC_STATE,
                            "Error: running with an unencrypted wallet, but "
                            "walletpassphrasechange was called.");
     }
 
     // TODO: get rid of these .c_str() calls by implementing
     // SecureString::operator=(std::string)
     // Alternately, find a way to make request.params[0] mlock()'d to begin
     // with.
     SecureString strOldWalletPass;
     strOldWalletPass.reserve(100);
     strOldWalletPass = request.params[0].get_str().c_str();
 
     SecureString strNewWalletPass;
     strNewWalletPass.reserve(100);
     strNewWalletPass = request.params[1].get_str().c_str();
 
     if (strOldWalletPass.empty() || strNewWalletPass.empty()) {
         throw JSONRPCError(RPC_INVALID_PARAMETER,
                            "passphrase can not be empty");
     }
 
     if (!pwallet->ChangeWalletPassphrase(strOldWalletPass, strNewWalletPass)) {
         throw JSONRPCError(
             RPC_WALLET_PASSPHRASE_INCORRECT,
             "Error: The wallet passphrase entered was incorrect.");
     }
 
     return NullUniValue;
 }
 
 static UniValue walletlock(const Config &config,
                            const JSONRPCRequest &request) {
     std::shared_ptr<CWallet> const wallet = GetWalletForJSONRPCRequest(request);
     CWallet *const pwallet = wallet.get();
 
     if (!EnsureWalletIsAvailable(pwallet, request.fHelp)) {
         return NullUniValue;
     }
 
     if (pwallet->IsCrypted() && (request.fHelp || request.params.size() != 0)) {
         throw std::runtime_error(RPCHelpMan{
             "walletlock",
             "\nRemoves the wallet encryption key from memory, locking the "
             "wallet.\n"
             "After calling this method, you will need to call walletpassphrase "
             "again\n"
             "before being able to call any methods which require the wallet to "
             "be unlocked.\n",
             {},
             RPCResults{},
             RPCExamples{
                 "\nSet the passphrase for 2 minutes to perform a "
                 "transaction\n" +
                 HelpExampleCli("walletpassphrase", "\"my pass phrase\" 120") +
                 "\nPerform a send (requires passphrase set)\n" +
                 HelpExampleCli("sendtoaddress",
                                "\"1M72Sfpbz1BPpXFHz9m3CdqATR44Jvaydd\" 1.0") +
                 "\nClear the passphrase since we are done before 2 minutes is "
                 "up\n" +
                 HelpExampleCli("walletlock", "") + "\nAs a JSON-RPC call\n" +
                 HelpExampleRpc("walletlock", "")},
         }
                                      .ToString());
     }
 
     auto locked_chain = pwallet->chain().lock();
     LOCK(pwallet->cs_wallet);
 
     if (request.fHelp) {
         return true;
     }
     if (!pwallet->IsCrypted()) {
         throw JSONRPCError(RPC_WALLET_WRONG_ENC_STATE,
                            "Error: running with an unencrypted wallet, but "
                            "walletlock was called.");
     }
 
     pwallet->Lock();
     pwallet->nRelockTime = 0;
 
     return NullUniValue;
 }
 
 static UniValue encryptwallet(const Config &config,
                               const JSONRPCRequest &request) {
     std::shared_ptr<CWallet> const wallet = GetWalletForJSONRPCRequest(request);
     CWallet *const pwallet = wallet.get();
 
     if (!EnsureWalletIsAvailable(pwallet, request.fHelp)) {
         return NullUniValue;
     }
 
     if (!pwallet->IsCrypted() &&
         (request.fHelp || request.params.size() != 1)) {
         throw std::runtime_error(RPCHelpMan{
             "encryptwallet",
             "\nEncrypts the wallet with 'passphrase'. This is for first time "
             "encryption.\n"
             "After this, any calls that interact with private keys such as "
             "sending or signing \n"
             "will require the passphrase to be set prior the making these "
             "calls.\n"
             "Use the walletpassphrase call for this, and then walletlock "
             "call.\n"
             "If the wallet is already encrypted, use the "
             "walletpassphrasechange call.\n",
             {
-                {"passphrase", RPCArg::Type::STR, /* opt */ false,
-                 /* default_val */ "",
+                {"passphrase", RPCArg::Type::STR, RPCArg::Optional::NO,
                  "The pass phrase to encrypt the wallet with. It must be "
                  "at least 1 character, but should be long."},
             },
             RPCResults{},
             RPCExamples{
                 "\nEncrypt your wallet\n" +
                 HelpExampleCli("encryptwallet", "\"my pass phrase\"") +
                 "\nNow set the passphrase to use the wallet, such as for "
                 "signing or sending bitcoin\n" +
                 HelpExampleCli("walletpassphrase", "\"my pass phrase\"") +
                 "\nNow we can do something like sign\n" +
                 HelpExampleCli("signmessage", "\"address\" \"test message\"") +
                 "\nNow lock the wallet again by removing the passphrase\n" +
                 HelpExampleCli("walletlock", "") + "\nAs a JSON-RPC call\n" +
                 HelpExampleRpc("encryptwallet", "\"my pass phrase\"")},
         }
                                      .ToString());
     }
 
     auto locked_chain = pwallet->chain().lock();
     LOCK(pwallet->cs_wallet);
 
     if (request.fHelp) {
         return true;
     }
     if (pwallet->IsCrypted()) {
         throw JSONRPCError(RPC_WALLET_WRONG_ENC_STATE,
                            "Error: running with an encrypted wallet, but "
                            "encryptwallet was called.");
     }
 
     // TODO: get rid of this .c_str() by implementing
     // SecureString::operator=(std::string)
     // Alternately, find a way to make request.params[0] mlock()'d to begin
     // with.
     SecureString strWalletPass;
     strWalletPass.reserve(100);
     strWalletPass = request.params[0].get_str().c_str();
 
     if (strWalletPass.empty()) {
         throw JSONRPCError(RPC_INVALID_PARAMETER,
                            "passphrase can not be empty");
     }
 
     if (!pwallet->EncryptWallet(strWalletPass)) {
         throw JSONRPCError(RPC_WALLET_ENCRYPTION_FAILED,
                            "Error: Failed to encrypt the wallet.");
     }
 
     return "wallet encrypted; The keypool has been flushed and a new HD seed "
            "was generated (if you are using HD). You need to make a new "
            "backup.";
 }
 
 static UniValue lockunspent(const Config &config,
                             const JSONRPCRequest &request) {
     std::shared_ptr<CWallet> const wallet = GetWalletForJSONRPCRequest(request);
     CWallet *const pwallet = wallet.get();
 
     if (!EnsureWalletIsAvailable(pwallet, request.fHelp)) {
         return NullUniValue;
     }
 
     if (request.fHelp || request.params.size() < 1 ||
         request.params.size() > 2) {
         throw std::runtime_error(RPCHelpMan{
             "lockunspent",
             "\nUpdates list of temporarily unspendable outputs.\n"
             "Temporarily lock (unlock=false) or unlock (unlock=true) specified "
             "transaction outputs.\n"
             "If no transaction outputs are specified when unlocking then all "
             "current locked transaction outputs are unlocked.\n"
             "A locked transaction output will not be chosen by automatic coin "
             "selection, when spending bitcoins.\n"
             "Locks are stored in memory only. Nodes start with zero locked "
             "outputs, and the locked output list\n"
             "is always cleared (by virtue of process exit) when a node stops "
             "or fails.\n"
             "Also see the listunspent call\n",
             {
-                {"unlock", RPCArg::Type::BOOL, /* opt */ false,
-                 /* default_val */ "",
+                {"unlock", RPCArg::Type::BOOL, RPCArg::Optional::NO,
                  "Whether to unlock (true) or lock (false) the specified "
                  "transactions"},
                 {
                     "transactions",
                     RPCArg::Type::ARR,
-                    /* opt */ true,
-                    /* default_val */ "empty array",
+                    /* default */ "empty array",
                     "A json array of objects. Each object the txid (string) "
                     "vout (numeric).",
                     {
                         {
                             "",
                             RPCArg::Type::OBJ,
-                            /* opt */ true,
-                            /* default_val */ "",
+                            RPCArg::Optional::OMITTED,
                             "",
                             {
                                 {"txid", RPCArg::Type::STR_HEX,
-                                 /* opt */ false, /* default_val */ "",
-                                 "The transaction id"},
-                                {"vout", RPCArg::Type::NUM, /* opt */ false,
-                                 /* default_val */ "", "The output number"},
+                                 RPCArg::Optional::NO, "The transaction id"},
+                                {"vout", RPCArg::Type::NUM,
+                                 RPCArg::Optional::NO, "The output number"},
                             },
                         },
                     },
                 },
             },
             RPCResult{"true|false    (boolean) Whether the command was "
                       "successful or not\n"},
             RPCExamples{"\nList the unspent transactions\n" +
                         HelpExampleCli("listunspent", "") +
                         "\nLock an unspent transaction\n" +
                         HelpExampleCli("lockunspent",
                                        "false "
                                        "\"[{\\\"txid\\\":"
                                        "\\\"a08e6907dbbd3d809776dbfc5d82e371"
                                        "b764ed838b5655e72f463568df1aadf0\\\""
                                        ",\\\"vout\\\":1}]\"") +
                         "\nList the locked transactions\n" +
                         HelpExampleCli("listlockunspent", "") +
                         "\nUnlock the transaction again\n" +
                         HelpExampleCli("lockunspent",
                                        "true "
                                        "\"[{\\\"txid\\\":"
                                        "\\\"a08e6907dbbd3d809776dbfc5d82e371"
                                        "b764ed838b5655e72f463568df1aadf0\\\""
                                        ",\\\"vout\\\":1}]\"") +
                         "\nAs a JSON-RPC call\n" +
                         HelpExampleRpc("lockunspent",
                                        "false, "
                                        "\"[{\\\"txid\\\":"
                                        "\\\"a08e6907dbbd3d809776dbfc5d82e371"
                                        "b764ed838b5655e72f463568df1aadf0\\\""
                                        ",\\\"vout\\\":1}]\"")},
         }
                                      .ToString());
     }
 
     // Make sure the results are valid at least up to the most recent block
     // the user could have gotten from another RPC command prior to now
     pwallet->BlockUntilSyncedToCurrentChain();
 
     auto locked_chain = pwallet->chain().lock();
     LOCK(pwallet->cs_wallet);
 
     RPCTypeCheckArgument(request.params[0], UniValue::VBOOL);
 
     bool fUnlock = request.params[0].get_bool();
 
     if (request.params[1].isNull()) {
         if (fUnlock) {
             pwallet->UnlockAllCoins();
         }
         return true;
     }
 
     RPCTypeCheckArgument(request.params[1], UniValue::VARR);
 
     const UniValue &output_params = request.params[1];
 
     // Create and validate the COutPoints first.
 
     std::vector<COutPoint> outputs;
     outputs.reserve(output_params.size());
 
     for (size_t idx = 0; idx < output_params.size(); idx++) {
         const UniValue &o = output_params[idx].get_obj();
 
         RPCTypeCheckObj(o, {
                                {"txid", UniValueType(UniValue::VSTR)},
                                {"vout", UniValueType(UniValue::VNUM)},
                            });
 
         const int nOutput = find_value(o, "vout").get_int();
         if (nOutput < 0) {
             throw JSONRPCError(RPC_INVALID_PARAMETER,
                                "Invalid parameter, vout must be positive");
         }
 
         const TxId txid(ParseHashO(o, "txid"));
         const auto it = pwallet->mapWallet.find(txid);
         if (it == pwallet->mapWallet.end()) {
             throw JSONRPCError(RPC_INVALID_PARAMETER,
                                "Invalid parameter, unknown transaction");
         }
 
         const COutPoint output(txid, nOutput);
         const CWalletTx &trans = it->second;
         if (output.GetN() >= trans.tx->vout.size()) {
             throw JSONRPCError(RPC_INVALID_PARAMETER,
                                "Invalid parameter, vout index out of bounds");
         }
 
         if (pwallet->IsSpent(*locked_chain, output)) {
             throw JSONRPCError(RPC_INVALID_PARAMETER,
                                "Invalid parameter, expected unspent output");
         }
 
         const bool is_locked = pwallet->IsLockedCoin(output);
         if (fUnlock && !is_locked) {
             throw JSONRPCError(RPC_INVALID_PARAMETER,
                                "Invalid parameter, expected locked output");
         }
 
         if (!fUnlock && is_locked) {
             throw JSONRPCError(RPC_INVALID_PARAMETER,
                                "Invalid parameter, output already locked");
         }
 
         outputs.push_back(output);
     }
 
     // Atomically set (un)locked status for the outputs.
     for (const COutPoint &output : outputs) {
         if (fUnlock) {
             pwallet->UnlockCoin(output);
         } else {
             pwallet->LockCoin(output);
         }
     }
 
     return true;
 }
 
 static UniValue listlockunspent(const Config &config,
                                 const JSONRPCRequest &request) {
     std::shared_ptr<CWallet> const wallet = GetWalletForJSONRPCRequest(request);
     CWallet *const pwallet = wallet.get();
 
     if (!EnsureWalletIsAvailable(pwallet, request.fHelp)) {
         return NullUniValue;
     }
 
     if (request.fHelp || request.params.size() > 0) {
         throw std::runtime_error(RPCHelpMan{
             "listlockunspent",
             "\nReturns list of temporarily unspendable outputs.\n"
             "See the lockunspent call to lock and unlock transactions for "
             "spending.\n",
             {},
             RPCResult{"[\n"
                       "  {\n"
                       "    \"txid\" : \"transactionid\",     (string) The "
                       "transaction id locked\n"
                       "    \"vout\" : n                      (numeric) The "
                       "vout value\n"
                       "  }\n"
                       "  ,...\n"
                       "]\n"},
             RPCExamples{"\nList the unspent transactions\n" +
                         HelpExampleCli("listunspent", "") +
                         "\nLock an unspent transaction\n" +
                         HelpExampleCli("lockunspent",
                                        "false "
                                        "\"[{\\\"txid\\\":"
                                        "\\\"a08e6907dbbd3d809776dbfc5d82e371"
                                        "b764ed838b5655e72f463568df1aadf0\\\""
                                        ",\\\"vout\\\":1}]\"") +
                         "\nList the locked transactions\n" +
                         HelpExampleCli("listlockunspent", "") +
                         "\nUnlock the transaction again\n" +
                         HelpExampleCli("lockunspent",
                                        "true "
                                        "\"[{\\\"txid\\\":"
                                        "\\\"a08e6907dbbd3d809776dbfc5d82e371"
                                        "b764ed838b5655e72f463568df1aadf0\\\""
                                        ",\\\"vout\\\":1}]\"") +
                         "\nAs a JSON-RPC call\n" +
                         HelpExampleRpc("listlockunspent", "")},
         }
                                      .ToString());
     }
 
     auto locked_chain = pwallet->chain().lock();
     LOCK(pwallet->cs_wallet);
 
     std::vector<COutPoint> vOutpts;
     pwallet->ListLockedCoins(vOutpts);
 
     UniValue ret(UniValue::VARR);
 
     for (const COutPoint &output : vOutpts) {
         UniValue o(UniValue::VOBJ);
 
         o.pushKV("txid", output.GetTxId().GetHex());
         o.pushKV("vout", int(output.GetN()));
         ret.push_back(o);
     }
 
     return ret;
 }
 
 static UniValue settxfee(const Config &config, const JSONRPCRequest &request) {
     std::shared_ptr<CWallet> const wallet = GetWalletForJSONRPCRequest(request);
     CWallet *const pwallet = wallet.get();
 
     if (!EnsureWalletIsAvailable(pwallet, request.fHelp)) {
         return NullUniValue;
     }
 
     if (request.fHelp || request.params.size() < 1 ||
         request.params.size() > 1) {
         throw std::runtime_error(RPCHelpMan{
             "settxfee",
             "\nSet the transaction fee per kB for this wallet. Overrides the "
             "global -paytxfee command line parameter.\n",
             {
-                {"amount", RPCArg::Type::AMOUNT, /* opt */ false,
-                 /* default_val */ "",
+                {"amount", RPCArg::Type::AMOUNT, RPCArg::Optional::NO,
                  "The transaction fee in " + CURRENCY_UNIT + "/kB"},
             },
             RPCResult{
                 "true|false        (boolean) Returns true if successful\n"},
             RPCExamples{HelpExampleCli("settxfee", "0.00001") +
                         HelpExampleRpc("settxfee", "0.00001")},
         }
                                      .ToString());
     }
 
     auto locked_chain = pwallet->chain().lock();
     LOCK(pwallet->cs_wallet);
 
     Amount nAmount = AmountFromValue(request.params[0]);
     CFeeRate tx_fee_rate(nAmount, 1000);
     if (tx_fee_rate == CFeeRate()) {
         // automatic selection
     } else if (tx_fee_rate < pwallet->chain().relayMinFee()) {
         throw JSONRPCError(
             RPC_INVALID_PARAMETER,
             strprintf("txfee cannot be less than min relay tx fee (%s)",
                       pwallet->chain().relayMinFee().ToString()));
     } else if (tx_fee_rate < pwallet->m_min_fee) {
         throw JSONRPCError(
             RPC_INVALID_PARAMETER,
             strprintf("txfee cannot be less than wallet min fee (%s)",
                       pwallet->m_min_fee.ToString()));
     }
 
     pwallet->m_pay_tx_fee = tx_fee_rate;
     return true;
 }
 
 static UniValue getwalletinfo(const Config &config,
                               const JSONRPCRequest &request) {
     std::shared_ptr<CWallet> const wallet = GetWalletForJSONRPCRequest(request);
     CWallet *const pwallet = wallet.get();
 
     if (!EnsureWalletIsAvailable(pwallet, request.fHelp)) {
         return NullUniValue;
     }
 
     if (request.fHelp || request.params.size() != 0) {
         throw std::runtime_error(RPCHelpMan{
             "getwalletinfo",
             "Returns an object containing various wallet state info.\n",
             {},
             RPCResult{
                 "{\n"
                 "  \"walletname\": xxxxx,             (string) the wallet "
                 "name\n"
                 "  \"walletversion\": xxxxx,          (numeric) the wallet "
                 "version\n"
                 "  \"balance\": xxxxxxx,              (numeric) the total "
                 "confirmed balance of the wallet in " +
                 CURRENCY_UNIT +
                 "\n"
                 "  \"unconfirmed_balance\": xxx,      (numeric) the total "
                 "unconfirmed balance of the wallet in " +
                 CURRENCY_UNIT +
                 "\n"
                 "  \"immature_balance\": xxxxxx,      (numeric) the total "
                 "immature balance of the wallet in " +
                 CURRENCY_UNIT +
                 "\n"
                 "  \"txcount\": xxxxxxx,              (numeric) the total "
                 "number of transactions in the wallet\n"
                 "  \"keypoololdest\": xxxxxx,         (numeric) the timestamp "
                 "(seconds since Unix epoch) of the oldest pre-generated key in "
                 "the key pool\n"
                 "  \"keypoolsize\": xxxx,             (numeric) how many new "
                 "keys are pre-generated (only counts external keys)\n"
                 "  \"keypoolsize_hd_internal\": xxxx, (numeric) how many new "
                 "keys are pre-generated for internal use (used for change "
                 "outputs, only appears if the wallet is using this feature, "
                 "otherwise external keys are used)\n"
                 "  \"unlocked_until\": ttt,           (numeric) the timestamp "
                 "in seconds since epoch (midnight Jan 1 1970 GMT) that the "
                 "wallet is unlocked for transfers, or 0 if the wallet is "
                 "locked\n"
                 "  \"paytxfee\": x.xxxx,              (numeric) the "
                 "transaction fee configuration, set in " +
                 CURRENCY_UNIT +
                 "/kB\n"
                 "  \"hdseedid\": \"<hash160>\"          (string, optional) the "
                 "Hash160 of the HD seed (only present when HD is enabled)\n"
                 "  \"hdmasterkeyid\": \"<hash160>\"     (string, optional) "
                 "alias for hdseedid retained for backwards-compatibility. Will "
                 "be removed in V0.21.\n"
                 "  \"private_keys_enabled\": true|false (boolean) false if "
                 "privatekeys are disabled for this wallet (enforced watch-only "
                 "wallet)\n"
                 "}\n"},
             RPCExamples{HelpExampleCli("getwalletinfo", "") +
                         HelpExampleRpc("getwalletinfo", "")},
         }
                                      .ToString());
     }
 
     // Make sure the results are valid at least up to the most recent block
     // the user could have gotten from another RPC command prior to now
     pwallet->BlockUntilSyncedToCurrentChain();
 
     auto locked_chain = pwallet->chain().lock();
     LOCK(pwallet->cs_wallet);
 
     UniValue obj(UniValue::VOBJ);
 
     size_t kpExternalSize = pwallet->KeypoolCountExternalKeys();
     obj.pushKV("walletname", pwallet->GetName());
     obj.pushKV("walletversion", pwallet->GetVersion());
     obj.pushKV("balance", ValueFromAmount(pwallet->GetBalance()));
     obj.pushKV("unconfirmed_balance",
                ValueFromAmount(pwallet->GetUnconfirmedBalance()));
     obj.pushKV("immature_balance",
                ValueFromAmount(pwallet->GetImmatureBalance()));
     obj.pushKV("txcount", (int)pwallet->mapWallet.size());
     obj.pushKV("keypoololdest", pwallet->GetOldestKeyPoolTime());
     obj.pushKV("keypoolsize", (int64_t)kpExternalSize);
     CKeyID seed_id = pwallet->GetHDChain().seed_id;
     if (!seed_id.IsNull() && pwallet->CanSupportFeature(FEATURE_HD_SPLIT)) {
         obj.pushKV("keypoolsize_hd_internal",
                    int64_t(pwallet->GetKeyPoolSize() - kpExternalSize));
     }
     if (pwallet->IsCrypted()) {
         obj.pushKV("unlocked_until", pwallet->nRelockTime);
     }
     obj.pushKV("paytxfee", ValueFromAmount(pwallet->m_pay_tx_fee.GetFeePerK()));
     if (!seed_id.IsNull()) {
         obj.pushKV("hdseedid", seed_id.GetHex());
         obj.pushKV("hdmasterkeyid", seed_id.GetHex());
     }
     obj.pushKV("private_keys_enabled",
                !pwallet->IsWalletFlagSet(WALLET_FLAG_DISABLE_PRIVATE_KEYS));
     return obj;
 }
 
 static UniValue listwalletdir(const Config &config,
                               const JSONRPCRequest &request) {
     if (request.fHelp || request.params.size() != 0) {
         throw std::runtime_error(RPCHelpMan{
             "listwalletdir",
             "Returns a list of wallets in the wallet directory.\n",
             {},
             RPCResult{
                 "{\n"
                 "  \"wallets\" : [                (json array of objects)\n"
                 "    {\n"
                 "      \"name\" : \"name\"          (string) The wallet name\n"
                 "    }\n"
                 "    ,...\n"
                 "  ]\n"
                 "}\n"},
             RPCExamples{HelpExampleCli("listwalletdir", "") +
                         HelpExampleRpc("listwalletdir", "")},
         }
                                      .ToString());
     }
 
     UniValue wallets(UniValue::VARR);
     for (const auto &path : ListWalletDir()) {
         UniValue wallet(UniValue::VOBJ);
         wallet.pushKV("name", path.string());
         wallets.push_back(wallet);
     }
 
     UniValue result(UniValue::VOBJ);
     result.pushKV("wallets", wallets);
     return result;
 }
 
 static UniValue listwallets(const Config &config,
                             const JSONRPCRequest &request) {
     if (request.fHelp || request.params.size() != 0) {
         throw std::runtime_error(RPCHelpMan{
             "listwallets",
             "Returns a list of currently loaded wallets.\n"
             "For full information on the wallet, use \"getwalletinfo\"\n",
             {},
             RPCResult{"[                         (json array of strings)\n"
                       "  \"walletname\"            (string) the wallet name\n"
                       "   ...\n"
                       "]\n"},
             RPCExamples{HelpExampleCli("listwallets", "") +
                         HelpExampleRpc("listwallets", "")},
         }
                                      .ToString());
     }
 
     UniValue obj(UniValue::VARR);
 
     for (const std::shared_ptr<CWallet> &wallet : GetWallets()) {
         if (!EnsureWalletIsAvailable(wallet.get(), request.fHelp)) {
             return NullUniValue;
         }
 
         LOCK(wallet->cs_wallet);
 
         obj.push_back(wallet->GetName());
     }
 
     return obj;
 }
 
 static UniValue loadwallet(const Config &config,
                            const JSONRPCRequest &request) {
     if (request.fHelp || request.params.size() != 1) {
         throw std::runtime_error(RPCHelpMan{
             "loadwallet",
             "\nLoads a wallet from a wallet file or directory."
             "\nNote that all wallet command-line options used when starting "
             "bitcoind will be"
             "\napplied to the new wallet (eg -zapwallettxes, upgradewallet, "
             "rescan, etc).\n",
             {
-                {"filename", RPCArg::Type::STR, /* opt */ false,
-                 /* default_val */ "", "The wallet directory or .dat file."},
+                {"filename", RPCArg::Type::STR, RPCArg::Optional::NO,
+                 "The wallet directory or .dat file."},
             },
             RPCResult{"{\n"
                       "  \"name\" :    <wallet_name>,        (string) The "
                       "wallet name if loaded successfully.\n"
                       "  \"warning\" : <warning>,            (string) Warning "
                       "message if wallet was not loaded cleanly.\n"
                       "}\n"},
             RPCExamples{HelpExampleCli("loadwallet", "\"test.dat\"") +
                         HelpExampleRpc("loadwallet", "\"test.dat\"")},
         }
                                      .ToString());
     }
 
     const CChainParams &chainParams = config.GetChainParams();
 
     WalletLocation location(request.params[0].get_str());
 
     if (!location.Exists()) {
         throw JSONRPCError(RPC_WALLET_NOT_FOUND,
                            "Wallet " + location.GetName() + " not found.");
     } else if (fs::is_directory(location.GetPath())) {
         // The given filename is a directory. Check that there's a wallet.dat
         // file.
         fs::path wallet_dat_file = location.GetPath() / "wallet.dat";
         if (fs::symlink_status(wallet_dat_file).type() == fs::file_not_found) {
             throw JSONRPCError(RPC_WALLET_NOT_FOUND,
                                "Directory " + location.GetName() +
                                    " does not contain a wallet.dat file.");
         }
     }
 
     std::string error, warning;
     std::shared_ptr<CWallet> const wallet =
         LoadWallet(chainParams, *g_rpc_node->chain, location, error, warning);
     if (!wallet) {
         throw JSONRPCError(RPC_WALLET_ERROR, error);
     }
 
     UniValue obj(UniValue::VOBJ);
     obj.pushKV("name", wallet->GetName());
     obj.pushKV("warning", warning);
 
     return obj;
 }
 
 static UniValue createwallet(const Config &config,
                              const JSONRPCRequest &request) {
     if (request.fHelp || request.params.size() < 1 ||
         request.params.size() > 3) {
         throw std::runtime_error(RPCHelpMan{
             "createwallet",
             "\nCreates and loads a new wallet.\n",
             {
-                {"wallet_name", RPCArg::Type::STR, /* opt */ false,
-                 /* default_val */ "",
+                {"wallet_name", RPCArg::Type::STR, RPCArg::Optional::NO,
                  "The name for the new wallet. If this is a path, "
                  "the wallet will be created at the path location."},
                 {"disable_private_keys", RPCArg::Type::BOOL,
-                 /* opt */ true, /* default_val */ "false",
+                 /* default */ "false",
                  "Disable the possibility of private keys (only "
                  "watchonlys are possible in this mode)."},
-                {"blank", RPCArg::Type::BOOL, /* opt */ true,
-                 /* default_val */ "false",
+                {"blank", RPCArg::Type::BOOL, /* default */ "false",
                  "Create a blank wallet. A blank wallet has no keys "
                  "or HD seed. One can be set using sethdseed.\n"},
             },
             RPCResult{
                 "{\n"
                 "  \"name\" :    <wallet_name>,        (string) The wallet "
                 "name if created successfully. If the wallet was created using "
                 "a full path, the wallet_name will be the full path.\n"
                 "  \"warning\" : <warning>,            (string) Warning "
                 "message if wallet was not loaded cleanly.\n"
                 "}\n"},
             RPCExamples{HelpExampleCli("createwallet", "\"testwallet\"") +
                         HelpExampleRpc("createwallet", "\"testwallet\"")},
         }
                                      .ToString());
     }
 
     const CChainParams &chainParams = config.GetChainParams();
 
     std::string error;
     std::string warning;
 
     uint64_t flags = 0;
     if (!request.params[1].isNull() && request.params[1].get_bool()) {
         flags |= WALLET_FLAG_DISABLE_PRIVATE_KEYS;
     }
 
     if (!request.params[2].isNull() && request.params[2].get_bool()) {
         flags |= WALLET_FLAG_BLANK_WALLET;
     }
 
     WalletLocation location(request.params[0].get_str());
     if (location.Exists()) {
         throw JSONRPCError(RPC_WALLET_ERROR,
                            "Wallet " + location.GetName() + " already exists.");
     }
 
     // Wallet::Verify will check if we're trying to create a wallet with a
     // duplicate name.
     if (!CWallet::Verify(chainParams, *g_rpc_node->chain, location, false,
                          error, warning)) {
         throw JSONRPCError(RPC_WALLET_ERROR,
                            "Wallet file verification failed: " + error);
     }
 
     std::shared_ptr<CWallet> const wallet = CWallet::CreateWalletFromFile(
         chainParams, *g_rpc_node->chain, location, flags);
     if (!wallet) {
         throw JSONRPCError(RPC_WALLET_ERROR, "Wallet creation failed.");
     }
     AddWallet(wallet);
 
     wallet->postInitProcess();
 
     UniValue obj(UniValue::VOBJ);
     obj.pushKV("name", wallet->GetName());
     obj.pushKV("warning", warning);
 
     return obj;
 }
 
 static UniValue unloadwallet(const Config &config,
                              const JSONRPCRequest &request) {
     if (request.fHelp || request.params.size() > 1) {
         throw std::runtime_error(RPCHelpMan{
             "unloadwallet",
             "Unloads the wallet referenced by the request endpoint "
             "otherwise unloads the wallet specified in the argument.\n"
             "Specifying the wallet name on a wallet endpoint is invalid.",
             {
-                {"wallet_name", RPCArg::Type::STR, /* opt */ true,
-                 /* default_val */ "the wallet name from the RPC request",
+                {"wallet_name", RPCArg::Type::STR,
+                 /* default */ "the wallet name from the RPC request",
                  "The name of the wallet to unload."},
             },
             RPCResults{},
             RPCExamples{HelpExampleCli("unloadwallet", "wallet_name") +
                         HelpExampleRpc("unloadwallet", "wallet_name")},
         }
                                      .ToString());
     }
 
     std::string wallet_name;
     if (GetWalletNameFromJSONRPCRequest(request, wallet_name)) {
         if (!request.params[0].isNull()) {
             throw JSONRPCError(RPC_INVALID_PARAMETER,
                                "Cannot unload the requested wallet");
         }
     } else {
         wallet_name = request.params[0].get_str();
     }
 
     std::shared_ptr<CWallet> wallet = GetWallet(wallet_name);
     if (!wallet) {
         throw JSONRPCError(RPC_WALLET_NOT_FOUND,
                            "Requested wallet does not exist or is not loaded");
     }
 
     // Release the "main" shared pointer and prevent further notifications.
     // Note that any attempt to load the same wallet would fail until the wallet
     // is destroyed (see CheckUniqueFileid).
     if (!RemoveWallet(wallet)) {
         throw JSONRPCError(RPC_MISC_ERROR, "Requested wallet already unloaded");
     }
 
     UnloadWallet(std::move(wallet));
 
     return NullUniValue;
 }
 
 static UniValue listunspent(const Config &config,
                             const JSONRPCRequest &request) {
     std::shared_ptr<CWallet> const wallet = GetWalletForJSONRPCRequest(request);
     CWallet *const pwallet = wallet.get();
 
     if (!EnsureWalletIsAvailable(pwallet, request.fHelp)) {
         return NullUniValue;
     }
 
     if (request.fHelp || request.params.size() > 5) {
         throw std::runtime_error(RPCHelpMan{
             "listunspent",
             "\nReturns array of unspent transaction outputs\n"
             "with between minconf and maxconf (inclusive) confirmations.\n"
             "Optionally filter to only include txouts paid to specified "
             "addresses.\n",
             {
-                {"minconf", RPCArg::Type::NUM, /* opt */ true,
-                 /* default_val */ "1", "The minimum confirmations to filter"},
-                {"maxconf", RPCArg::Type::NUM, /* opt */ true,
-                 /* default_val */ "9999999",
+                {"minconf", RPCArg::Type::NUM, /* default */ "1",
+                 "The minimum confirmations to filter"},
+                {"maxconf", RPCArg::Type::NUM, /* default */ "9999999",
                  "The maximum confirmations to filter"},
                 {
                     "addresses",
                     RPCArg::Type::ARR,
-                    /* opt */ true,
-                    /* default_val */ "empty array",
+                    /* default */ "empty array",
                     "A json array of bitcoin addresses to filter",
                     {
-                        {"address", RPCArg::Type::STR, /* opt */ true,
-                         /* default_val */ "", "bitcoin address"},
+                        {"address", RPCArg::Type::STR,
+                         RPCArg::Optional::OMITTED, "bitcoin address"},
                     },
                 },
-                {"include_unsafe", RPCArg::Type::BOOL, /* opt */ true,
-                 /* default_val */ "true",
+                {"include_unsafe", RPCArg::Type::BOOL, /* default */ "true",
                  "Include outputs that are not safe to spend\n"
                  "                  See description of \"safe\" attribute "
                  "below."},
                 {"query_options",
                  RPCArg::Type::OBJ,
-                 /* opt */ true,
-                 /* default_val */ "null",
+                 RPCArg::Optional::OMITTED_NAMED_ARG,
                  "JSON with query options",
                  {
-                     {"minimumAmount", RPCArg::Type::AMOUNT, /* opt */ true,
-                      /* default_val */ "0",
+                     {"minimumAmount", RPCArg::Type::AMOUNT, /* default */ "0",
                       "Minimum value of each UTXO in " + CURRENCY_UNIT + ""},
-                     {"maximumAmount", RPCArg::Type::AMOUNT, /* opt */ true,
-                      /* default_val */ "unlimited",
+                     {"maximumAmount", RPCArg::Type::AMOUNT,
+                      /* default */ "unlimited",
                       "Maximum value of each UTXO in " + CURRENCY_UNIT + ""},
-                     {"maximumCount", RPCArg::Type::NUM, /* opt */ true,
-                      /* default_val */ "unlimited", "Maximum number of UTXOs"},
+                     {"maximumCount", RPCArg::Type::NUM,
+                      /* default */ "unlimited", "Maximum number of UTXOs"},
                      {"minimumSumAmount", RPCArg::Type::AMOUNT,
-                      /* opt */ true, /* default_val */ "unlimited",
+                      /* default */ "unlimited",
                       "Minimum sum value of all UTXOs in " + CURRENCY_UNIT +
                           ""},
                  },
                  "query_options"},
             },
             RPCResult{
                 "[                   (array of json object)\n"
                 "  {\n"
                 "    \"txid\" : \"txid\",          (string) the transaction id "
                 "\n"
                 "    \"vout\" : n,               (numeric) the vout value\n"
                 "    \"address\" : \"address\",    (string) the bitcoin "
                 "address\n"
                 "    \"label\" : \"label\",        (string) The associated "
                 "label, or \"\" for the default label\n"
                 "    \"scriptPubKey\" : \"key\",   (string) the script key\n"
                 "    \"amount\" : x.xxx,         (numeric) the transaction "
                 "output amount in " +
                 CURRENCY_UNIT +
                 "\n"
                 "    \"confirmations\" : n,      (numeric) The number of "
                 "confirmations\n"
                 "    \"redeemScript\" : n        (string) The redeemScript if "
                 "scriptPubKey is P2SH\n"
                 "    \"spendable\" : xxx,        (bool) Whether we have the "
                 "private keys to spend this output\n"
                 "    \"solvable\" : xxx,         (bool) Whether we know how to "
                 "spend this output, ignoring the lack of keys\n"
                 "    \"desc\" : xxx,             (string, only when solvable) "
                 "A descriptor for spending this output\n"
                 "    \"safe\" : xxx              (bool) Whether this output is "
                 "considered safe to spend. Unconfirmed transactions\n"
                 "                              from outside keys are "
                 "considered unsafe and are not eligible for spending by\n"
                 "                              fundrawtransaction and "
                 "sendtoaddress.\n"
                 "  }\n"
                 "  ,...\n"
                 "]\n"},
             RPCExamples{
                 HelpExampleCli("listunspent", "") +
                 HelpExampleCli(
                     "listunspent",
                     "6 9999999 "
                     "\"[\\\"1PGFqEzfmQch1gKD3ra4k18PNj3tTUUSqg\\\","
                     "\\\"1LtvqCaApEdUGFkpKMM4MstjcaL4dKg8SP\\\"]\"") +
                 HelpExampleRpc(
                     "listunspent",
                     "6, 9999999 "
                     "\"[\\\"1PGFqEzfmQch1gKD3ra4k18PNj3tTUUSqg\\\","
                     "\\\"1LtvqCaApEdUGFkpKMM4MstjcaL4dKg8SP\\\"]\"") +
                 HelpExampleCli(
                     "listunspent",
                     "6 9999999 '[]' true '{ \"minimumAmount\": 0.005 }'") +
                 HelpExampleRpc(
                     "listunspent",
                     "6, 9999999, [] , true, { \"minimumAmount\": 0.005 } ")},
         }
                                      .ToString());
     }
 
     int nMinDepth = 1;
     if (!request.params[0].isNull()) {
         RPCTypeCheckArgument(request.params[0], UniValue::VNUM);
         nMinDepth = request.params[0].get_int();
     }
 
     int nMaxDepth = 9999999;
     if (!request.params[1].isNull()) {
         RPCTypeCheckArgument(request.params[1], UniValue::VNUM);
         nMaxDepth = request.params[1].get_int();
     }
 
     std::set<CTxDestination> destinations;
     if (!request.params[2].isNull()) {
         RPCTypeCheckArgument(request.params[2], UniValue::VARR);
         UniValue inputs = request.params[2].get_array();
         for (size_t idx = 0; idx < inputs.size(); idx++) {
             const UniValue &input = inputs[idx];
             CTxDestination dest =
                 DecodeDestination(input.get_str(), config.GetChainParams());
             if (!IsValidDestination(dest)) {
                 throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY,
                                    std::string("Invalid Bitcoin address: ") +
                                        input.get_str());
             }
             if (!destinations.insert(dest).second) {
                 throw JSONRPCError(
                     RPC_INVALID_PARAMETER,
                     std::string("Invalid parameter, duplicated address: ") +
                         input.get_str());
             }
         }
     }
 
     bool include_unsafe = true;
     if (!request.params[3].isNull()) {
         RPCTypeCheckArgument(request.params[3], UniValue::VBOOL);
         include_unsafe = request.params[3].get_bool();
     }
 
     Amount nMinimumAmount = Amount::zero();
     Amount nMaximumAmount = MAX_MONEY;
     Amount nMinimumSumAmount = MAX_MONEY;
     uint64_t nMaximumCount = 0;
 
     if (!request.params[4].isNull()) {
         const UniValue &options = request.params[4].get_obj();
 
         if (options.exists("minimumAmount")) {
             nMinimumAmount = AmountFromValue(options["minimumAmount"]);
         }
 
         if (options.exists("maximumAmount")) {
             nMaximumAmount = AmountFromValue(options["maximumAmount"]);
         }
 
         if (options.exists("minimumSumAmount")) {
             nMinimumSumAmount = AmountFromValue(options["minimumSumAmount"]);
         }
 
         if (options.exists("maximumCount")) {
             nMaximumCount = options["maximumCount"].get_int64();
         }
     }
 
     // Make sure the results are valid at least up to the most recent block
     // the user could have gotten from another RPC command prior to now
     pwallet->BlockUntilSyncedToCurrentChain();
 
     UniValue results(UniValue::VARR);
     std::vector<COutput> vecOutputs;
     {
         auto locked_chain = pwallet->chain().lock();
         LOCK(pwallet->cs_wallet);
         pwallet->AvailableCoins(*locked_chain, vecOutputs, !include_unsafe,
                                 nullptr, nMinimumAmount, nMaximumAmount,
                                 nMinimumSumAmount, nMaximumCount, nMinDepth,
                                 nMaxDepth);
     }
 
     LOCK(pwallet->cs_wallet);
 
     for (const COutput &out : vecOutputs) {
         CTxDestination address;
         const CScript &scriptPubKey = out.tx->tx->vout[out.i].scriptPubKey;
         bool fValidAddress = ExtractDestination(scriptPubKey, address);
 
         if (destinations.size() &&
             (!fValidAddress || !destinations.count(address))) {
             continue;
         }
 
         UniValue entry(UniValue::VOBJ);
         entry.pushKV("txid", out.tx->GetId().GetHex());
         entry.pushKV("vout", out.i);
 
         if (fValidAddress) {
             entry.pushKV("address", EncodeDestination(address, config));
 
             auto i = pwallet->mapAddressBook.find(address);
             if (i != pwallet->mapAddressBook.end()) {
                 entry.pushKV("label", i->second.name);
             }
 
             if (scriptPubKey.IsPayToScriptHash()) {
                 const CScriptID &hash = boost::get<CScriptID>(address);
                 CScript redeemScript;
                 if (pwallet->GetCScript(hash, redeemScript)) {
                     entry.pushKV("redeemScript", HexStr(redeemScript.begin(),
                                                         redeemScript.end()));
                 }
             }
         }
 
         entry.pushKV("scriptPubKey",
                      HexStr(scriptPubKey.begin(), scriptPubKey.end()));
         entry.pushKV("amount", ValueFromAmount(out.tx->tx->vout[out.i].nValue));
         entry.pushKV("confirmations", out.nDepth);
         entry.pushKV("spendable", out.fSpendable);
         entry.pushKV("solvable", out.fSolvable);
         if (out.fSolvable) {
             auto descriptor = InferDescriptor(scriptPubKey, *pwallet);
             entry.pushKV("desc", descriptor->ToString());
         }
         entry.pushKV("safe", out.fSafe);
         results.push_back(entry);
     }
 
     return results;
 }
 
 void FundTransaction(CWallet *const pwallet, CMutableTransaction &tx,
                      Amount &fee_out, int &change_position, UniValue options) {
     // Make sure the results are valid at least up to the most recent block
     // the user could have gotten from another RPC command prior to now
     pwallet->BlockUntilSyncedToCurrentChain();
 
     CCoinControl coinControl;
     change_position = -1;
     bool lockUnspents = false;
     UniValue subtractFeeFromOutputs;
     std::set<int> setSubtractFeeFromOutputs;
 
     if (!options.isNull()) {
         if (options.type() == UniValue::VBOOL) {
             // backward compatibility bool only fallback
             coinControl.fAllowWatchOnly = options.get_bool();
         } else {
             RPCTypeCheckArgument(options, UniValue::VOBJ);
             RPCTypeCheckObj(
                 options,
                 {
                     {"changeAddress", UniValueType(UniValue::VSTR)},
                     {"changePosition", UniValueType(UniValue::VNUM)},
                     {"includeWatching", UniValueType(UniValue::VBOOL)},
                     {"lockUnspents", UniValueType(UniValue::VBOOL)},
                     // will be checked below
                     {"feeRate", UniValueType()},
                     {"subtractFeeFromOutputs", UniValueType(UniValue::VARR)},
                 },
                 true, true);
 
             if (options.exists("changeAddress")) {
                 CTxDestination dest = DecodeDestination(
                     options["changeAddress"].get_str(), pwallet->chainParams);
 
                 if (!IsValidDestination(dest)) {
                     throw JSONRPCError(
                         RPC_INVALID_ADDRESS_OR_KEY,
                         "changeAddress must be a valid bitcoin address");
                 }
 
                 coinControl.destChange = dest;
             }
 
             if (options.exists("changePosition")) {
                 change_position = options["changePosition"].get_int();
             }
 
             if (options.exists("includeWatching")) {
                 coinControl.fAllowWatchOnly =
                     options["includeWatching"].get_bool();
             }
 
             if (options.exists("lockUnspents")) {
                 lockUnspents = options["lockUnspents"].get_bool();
             }
 
             if (options.exists("feeRate")) {
                 coinControl.m_feerate =
                     CFeeRate(AmountFromValue(options["feeRate"]));
                 coinControl.fOverrideFeeRate = true;
             }
 
             if (options.exists("subtractFeeFromOutputs")) {
                 subtractFeeFromOutputs =
                     options["subtractFeeFromOutputs"].get_array();
             }
         }
     }
 
     if (tx.vout.size() == 0) {
         throw JSONRPCError(RPC_INVALID_PARAMETER,
                            "TX must have at least one output");
     }
 
     if (change_position != -1 &&
         (change_position < 0 ||
          (unsigned int)change_position > tx.vout.size())) {
         throw JSONRPCError(RPC_INVALID_PARAMETER,
                            "changePosition out of bounds");
     }
 
     for (size_t idx = 0; idx < subtractFeeFromOutputs.size(); idx++) {
         int pos = subtractFeeFromOutputs[idx].get_int();
         if (setSubtractFeeFromOutputs.count(pos)) {
             throw JSONRPCError(
                 RPC_INVALID_PARAMETER,
                 strprintf("Invalid parameter, duplicated position: %d", pos));
         }
         if (pos < 0) {
             throw JSONRPCError(
                 RPC_INVALID_PARAMETER,
                 strprintf("Invalid parameter, negative position: %d", pos));
         }
         if (pos >= int(tx.vout.size())) {
             throw JSONRPCError(
                 RPC_INVALID_PARAMETER,
                 strprintf("Invalid parameter, position too large: %d", pos));
         }
         setSubtractFeeFromOutputs.insert(pos);
     }
 
     std::string strFailReason;
 
     if (!pwallet->FundTransaction(tx, fee_out, change_position, strFailReason,
                                   lockUnspents, setSubtractFeeFromOutputs,
                                   coinControl)) {
         throw JSONRPCError(RPC_WALLET_ERROR, strFailReason);
     }
 }
 
 static UniValue fundrawtransaction(const Config &config,
                                    const JSONRPCRequest &request) {
     std::shared_ptr<CWallet> const wallet = GetWalletForJSONRPCRequest(request);
     CWallet *const pwallet = wallet.get();
 
     if (!EnsureWalletIsAvailable(pwallet, request.fHelp)) {
         return NullUniValue;
     }
 
     if (request.fHelp || request.params.size() < 1 ||
         request.params.size() > 2) {
         throw std::runtime_error(RPCHelpMan{
             "fundrawtransaction",
             "\nAdd inputs to a transaction until it has enough in value to "
             "meet its out value.\n"
             "This will not modify existing inputs, and will add at most one "
             "change output to the outputs.\n"
             "No existing outputs will be modified unless "
             "\"subtractFeeFromOutputs\" is specified.\n"
             "Note that inputs which were signed may need to be resigned after "
             "completion since in/outputs have been added.\n"
             "The inputs added will not be signed, use "
             "signrawtransactionwithkey or signrawtransactionwithwallet for "
             "that.\n"
             "Note that all existing inputs must have their previous output "
             "transaction be in the wallet.\n"
             "Note that all inputs selected must be of standard form and P2SH "
             "scripts must be\n"
             "in the wallet using importaddress or addmultisigaddress (to "
             "calculate fees).\n"
             "You can see whether this is the case by checking the \"solvable\" "
             "field in the listunspent output.\n"
             "Only pay-to-pubkey, multisig, and P2SH versions thereof are "
             "currently supported for watch-only\n",
             {
-                {"hexstring", RPCArg::Type::STR_HEX, /* opt */ false,
-                 /* default_val */ "", "The hex string of the raw transaction"},
+                {"hexstring", RPCArg::Type::STR_HEX, RPCArg::Optional::NO,
+                 "The hex string of the raw transaction"},
                 {"options",
                  RPCArg::Type::OBJ,
-                 /* opt */ true,
-                 /* default_val */ "null",
+                 RPCArg::Optional::OMITTED_NAMED_ARG,
                  "for backward compatibility: passing in a true instead of an "
                  "object will result in {\"includeWatching\":true}",
                  {
-                     {"changeAddress", RPCArg::Type::STR, /* opt */ true,
-                      /* default_val */ "pool address",
+                     {"changeAddress", RPCArg::Type::STR,
+                      /* default */ "pool address",
                       "The bitcoin address to receive the change"},
-                     {"changePosition", RPCArg::Type::NUM, /* opt */ true,
-                      /* default_val */ "", "The index of the change output"},
-                     {"includeWatching", RPCArg::Type::BOOL, /* opt */ true,
-                      /* default_val */ "false",
+                     {"changePosition", RPCArg::Type::NUM, /* default */ "",
+                      "The index of the change output"},
+                     {"includeWatching", RPCArg::Type::BOOL,
+                      /* default */ "false",
                       "Also select inputs which are watch only"},
-                     {"lockUnspents", RPCArg::Type::BOOL, /* opt */ true,
-                      /* default_val */ "false",
+                     {"lockUnspents", RPCArg::Type::BOOL, /* default */ "false",
                       "Lock selected unspent outputs"},
-                     {"feeRate", RPCArg::Type::AMOUNT, /* opt */ true,
-                      /* default_val */
+                     {"feeRate", RPCArg::Type::AMOUNT, /* default */
                       "not set: makes wallet determine the fee",
                       "Set a specific fee rate in " + CURRENCY_UNIT + "/kB"},
                      {
                          "subtractFeeFromOutputs",
                          RPCArg::Type::ARR,
-                         /* opt */ true,
-                         /* default_val */ "empty array",
+                         /* default */ "empty array",
                          "A json array of integers.\n"
                          "                              The fee will be "
                          "equally deducted from the amount of each "
                          "specified output.\n"
                          "                              Those recipients "
                          "will receive less bitcoins than you enter in "
                          "their corresponding amount field.\n"
                          "                              If no outputs are "
                          "specified here, the sender pays the fee.",
                          {
                              {"vout_index", RPCArg::Type::NUM,
-                              /* opt */ true, /* default_val */ "",
+                              RPCArg::Optional::OMITTED,
                               "The zero-based output index, before a "
                               "change output is added."},
                          },
                      },
                  },
                  "options"},
             },
             RPCResult{"{\n"
                       "  \"hex\":       \"value\", (string)  The resulting raw "
                       "transaction (hex-encoded string)\n"
                       "  \"fee\":       n,         (numeric) Fee in " +
                       CURRENCY_UNIT +
                       " the resulting transaction pays\n"
                       "  \"changepos\": n          (numeric) The position of "
                       "the added change output, or -1\n"
                       "}\n"},
             RPCExamples{
                 "\nCreate a transaction with no inputs\n" +
                 HelpExampleCli("createrawtransaction",
                                "\"[]\" \"{\\\"myaddress\\\":0.01}\"") +
                 "\nAdd sufficient unsigned inputs to meet the output value\n" +
                 HelpExampleCli("fundrawtransaction", "\"rawtransactionhex\"") +
                 "\nSign the transaction\n" +
                 HelpExampleCli("signrawtransactionwithwallet",
                                "\"fundedtransactionhex\"") +
                 "\nSend the transaction\n" +
                 HelpExampleCli("sendrawtransaction",
                                "\"signedtransactionhex\"")},
         }
                                      .ToString());
     }
 
     RPCTypeCheck(request.params, {UniValue::VSTR, UniValueType()});
 
     // parse hex string from parameter
     CMutableTransaction tx;
     if (!DecodeHexTx(tx, request.params[0].get_str())) {
         throw JSONRPCError(RPC_DESERIALIZATION_ERROR, "TX decode failed");
     }
 
     Amount fee;
     int change_position;
     FundTransaction(pwallet, tx, fee, change_position, request.params[1]);
 
     UniValue result(UniValue::VOBJ);
     result.pushKV("hex", EncodeHexTx(CTransaction(tx)));
     result.pushKV("fee", ValueFromAmount(fee));
     result.pushKV("changepos", change_position);
 
     return result;
 }
 
 UniValue signrawtransactionwithwallet(const Config &config,
                                       const JSONRPCRequest &request) {
     std::shared_ptr<CWallet> const wallet = GetWalletForJSONRPCRequest(request);
     CWallet *const pwallet = wallet.get();
 
     if (!EnsureWalletIsAvailable(pwallet, request.fHelp)) {
         return NullUniValue;
     }
 
     if (request.fHelp || request.params.size() < 1 ||
         request.params.size() > 3) {
         throw std::runtime_error(RPCHelpMan{
             "signrawtransactionwithwallet",
             "\nSign inputs for raw transaction (serialized, hex-encoded).\n"
             "The second optional argument (may be null) is an array of "
             "previous transaction outputs that\n"
             "this transaction depends on but may not yet be in the block "
             "chain.\n" +
                 HelpRequiringPassphrase(pwallet) + "\n",
             {
-                {"hexstring", RPCArg::Type::STR, /* opt */ false,
-                 /* default_val */ "", "The transaction hex string"},
+                {"hexstring", RPCArg::Type::STR, RPCArg::Optional::NO,
+                 "The transaction hex string"},
                 {
                     "prevtxs",
                     RPCArg::Type::ARR,
-                    /* opt */ true,
-                    /* default_val */ "null",
+                    RPCArg::Optional::OMITTED_NAMED_ARG,
                     "A json array of previous dependent transaction outputs",
                     {
                         {
                             "",
                             RPCArg::Type::OBJ,
-                            /* opt */ false,
-                            /* default_val */ "",
+                            RPCArg::Optional::OMITTED,
                             "",
                             {
                                 {"txid", RPCArg::Type::STR_HEX,
-                                 /* opt */ false, /* default_val */ "",
-                                 "The transaction id"},
-                                {"vout", RPCArg::Type::NUM, /* opt */ false,
-                                 /* default_val */ "", "The output number"},
+                                 RPCArg::Optional::NO, "The transaction id"},
+                                {"vout", RPCArg::Type::NUM,
+                                 RPCArg::Optional::NO, "The output number"},
                                 {"scriptPubKey", RPCArg::Type::STR_HEX,
-                                 /* opt */ false, /* default_val */ "",
-                                 "script key"},
+                                 RPCArg::Optional::NO, "script key"},
                                 {"redeemScript", RPCArg::Type::STR_HEX,
-                                 /* opt */ true, /* default_val */ "omitted",
+                                 RPCArg::Optional::OMITTED,
                                  "(required for P2SH)"},
                                 {"amount", RPCArg::Type::AMOUNT,
-                                 /* opt */ false, /* default_val */ "",
-                                 "The amount spent"},
+                                 RPCArg::Optional::NO, "The amount spent"},
                             },
                         },
                     },
                 },
-                {"sighashtype", RPCArg::Type::STR, /* opt */ true,
-                 /* default_val */ "ALL|FORKID",
+                {"sighashtype", RPCArg::Type::STR, /* default */ "ALL|FORKID",
                  "The signature hash type. Must be one of\n"
                  "       \"ALL|FORKID\"\n"
                  "       \"NONE|FORKID\"\n"
                  "       \"SINGLE|FORKID\"\n"
                  "       \"ALL|FORKID|ANYONECANPAY\"\n"
                  "       \"NONE|FORKID|ANYONECANPAY\"\n"
                  "       \"SINGLE|FORKID|ANYONECANPAY\""},
             },
             RPCResult{"{\n"
                       "  \"hex\" : \"value\",                  (string) The "
                       "hex-encoded raw transaction with signature(s)\n"
                       "  \"complete\" : true|false,          (boolean) If the "
                       "transaction has a complete set of signatures\n"
                       "  \"errors\" : [                      (json array of "
                       "objects) Script verification errors (if there are any)\n"
                       "    {\n"
                       "      \"txid\" : \"hash\",              (string) The "
                       "hash of the referenced, previous transaction\n"
                       "      \"vout\" : n,                   (numeric) The "
                       "index of the output to spent and used as input\n"
                       "      \"scriptSig\" : \"hex\",          (string) The "
                       "hex-encoded signature script\n"
                       "      \"sequence\" : n,               (numeric) Script "
                       "sequence number\n"
                       "      \"error\" : \"text\"              (string) "
                       "Verification or signing error related to the input\n"
                       "    }\n"
                       "    ,...\n"
                       "  ]\n"
                       "}\n"},
             RPCExamples{
                 HelpExampleCli("signrawtransactionwithwallet", "\"myhex\"") +
                 HelpExampleRpc("signrawtransactionwithwallet", "\"myhex\"")},
         }
                                      .ToString());
     }
 
     RPCTypeCheck(request.params,
                  {UniValue::VSTR, UniValue::VARR, UniValue::VSTR}, true);
 
     CMutableTransaction mtx;
     if (!DecodeHexTx(mtx, request.params[0].get_str())) {
         throw JSONRPCError(RPC_DESERIALIZATION_ERROR, "TX decode failed");
     }
 
     // Sign the transaction
     auto locked_chain = pwallet->chain().lock();
     LOCK(pwallet->cs_wallet);
     EnsureWalletIsUnlocked(pwallet);
 
     return SignTransaction(pwallet->chain(), mtx, request.params[1], pwallet,
                            false, request.params[2]);
 }
 
 UniValue generate(const Config &config, const JSONRPCRequest &request) {
     std::shared_ptr<CWallet> const wallet = GetWalletForJSONRPCRequest(request);
     CWallet *const pwallet = wallet.get();
 
     if (!EnsureWalletIsAvailable(pwallet, request.fHelp)) {
         return NullUniValue;
     }
 
     if (request.fHelp || request.params.size() < 1 ||
         request.params.size() > 2) {
         throw std::runtime_error(RPCHelpMan{
             "generate",
             "\nMine up to nblocks blocks immediately (before the RPC call "
             "returns) to an address in the wallet.\n",
             {
-                {"nblocks", RPCArg::Type::NUM, /* opt */ false,
-                 /* default_val */ "",
+                {"nblocks", RPCArg::Type::NUM, RPCArg::Optional::NO,
                  "How many blocks are generated immediately."},
-                {"maxtries", RPCArg::Type::NUM, /* opt */ true,
-                 /* default_val */ "1000000", "How many iterations to try."},
+                {"maxtries", RPCArg::Type::NUM, /* default */ "1000000",
+                 "How many iterations to try."},
             },
             RPCResult{
                 "[ blockhashes ]     (array) hashes of blocks generated\n"},
             RPCExamples{"\nGenerate 11 blocks\n" +
                         HelpExampleCli("generate", "11")}}
                                      .ToString());
     }
 
     if (!IsDeprecatedRPCEnabled(gArgs, "generate")) {
         throw JSONRPCError(RPC_METHOD_DEPRECATED,
                            "The wallet generate rpc method is deprecated and "
                            "will be fully removed in v0.22. "
                            "To use generate in v0.21, restart bitcoind with "
                            "-deprecatedrpc=generate.\n"
                            "Clients should transition to using the node rpc "
                            "method generatetoaddress\n");
     }
 
     int num_generate = request.params[0].get_int();
     uint64_t max_tries = 1000000;
     if (!request.params[1].isNull()) {
         max_tries = request.params[1].get_int();
     }
 
     std::shared_ptr<CReserveScript> coinbase_script;
     pwallet->GetScriptForMining(coinbase_script);
 
     // If the keypool is exhausted, no script is returned at all.  Catch this.
     if (!coinbase_script) {
         throw JSONRPCError(
             RPC_WALLET_KEYPOOL_RAN_OUT,
             "Error: Keypool ran out, please call keypoolrefill first");
     }
 
     // throw an error if no script was provided
     if (coinbase_script->reserveScript.empty()) {
         throw JSONRPCError(RPC_INTERNAL_ERROR, "No coinbase script available");
     }
 
     return generateBlocks(config, coinbase_script, num_generate, max_tries,
                           true);
 }
 
 UniValue rescanblockchain(const Config &config, const JSONRPCRequest &request) {
     std::shared_ptr<CWallet> const wallet = GetWalletForJSONRPCRequest(request);
     CWallet *const pwallet = wallet.get();
 
     if (!EnsureWalletIsAvailable(pwallet, request.fHelp)) {
         return NullUniValue;
     }
 
     if (request.fHelp || request.params.size() > 2) {
         throw std::runtime_error(RPCHelpMan{
             "rescanblockchain",
             "\nRescan the local blockchain for wallet related transactions.\n",
             {
-                {"start_height", RPCArg::Type::NUM, /* opt */ true,
-                 /* default_val */ "0",
+                {"start_height", RPCArg::Type::NUM, /* default */ "0",
                  "block height where the rescan should start"},
-                {"stop_height", RPCArg::Type::NUM, /* opt */ true,
-                 /* default_val */ "tip height",
+                {"stop_height", RPCArg::Type::NUM,
+                 RPCArg::Optional::OMITTED_NAMED_ARG,
                  "the last block height that should be scanned"},
             },
             RPCResult{"{\n"
                       "  \"start_height\"     (numeric) The block height where "
                       "the rescan started (the requested height or 0\n"
                       "  \"stop_height\"      (numeric) The height of the last "
                       "rescanned block. May be null in rare cases if there was "
                       "a reorg and the call didn't scan any blocks because "
                       "they were already scanned in the background.\n"
                       "}\n"},
             RPCExamples{HelpExampleCli("rescanblockchain", "100000 120000") +
                         HelpExampleRpc("rescanblockchain", "100000, 120000")},
         }
                                      .ToString());
     }
 
     WalletRescanReserver reserver(pwallet);
     if (!reserver.reserve()) {
         throw JSONRPCError(
             RPC_WALLET_ERROR,
             "Wallet is currently rescanning. Abort existing rescan or wait.");
     }
 
     int start_height = 0;
     BlockHash start_block, stop_block;
     {
         auto locked_chain = pwallet->chain().lock();
         Optional<int> tip_height = locked_chain->getHeight();
 
         if (!request.params[0].isNull()) {
             start_height = request.params[0].get_int();
             if (start_height < 0 || !tip_height || start_height > *tip_height) {
                 throw JSONRPCError(RPC_INVALID_PARAMETER,
                                    "Invalid start_height");
             }
         }
 
         Optional<int> stop_height;
         if (!request.params[1].isNull()) {
             stop_height = request.params[1].get_int();
             if (*stop_height < 0 || !tip_height || *stop_height > *tip_height) {
                 throw JSONRPCError(RPC_INVALID_PARAMETER,
                                    "Invalid stop_height");
             } else if (*stop_height < start_height) {
                 throw JSONRPCError(
                     RPC_INVALID_PARAMETER,
                     "stop_height must be greater than start_height");
             }
         }
 
         // We can't rescan beyond non-pruned blocks, stop and throw an error
         if (locked_chain->findPruned(start_height, stop_height)) {
             throw JSONRPCError(
                 RPC_MISC_ERROR,
                 "Can't rescan beyond pruned data. Use RPC call "
                 "getblockchaininfo to determine your pruned height.");
         }
 
         if (tip_height) {
             start_block = locked_chain->getBlockHash(start_height);
 
             // If called with a stop_height, set the stop_height here to
             // trigger a rescan to that height.
             // If called without a stop height, leave stop_height as null here
             // so rescan continues to the tip (even if the tip advances during
             // rescan).
             if (stop_height) {
                 stop_block = locked_chain->getBlockHash(*stop_height);
             }
         }
     }
 
     CWallet::ScanResult result = pwallet->ScanForWalletTransactions(
         start_block, stop_block, reserver, true /* fUpdate */);
     switch (result.status) {
         case CWallet::ScanResult::SUCCESS:
             break;
         case CWallet::ScanResult::FAILURE:
             throw JSONRPCError(
                 RPC_MISC_ERROR,
                 "Rescan failed. Potentially corrupted data files.");
         case CWallet::ScanResult::USER_ABORT:
             throw JSONRPCError(RPC_MISC_ERROR, "Rescan aborted.");
             // no default case, so the compiler can warn about missing cases
     }
     UniValue response(UniValue::VOBJ);
     response.pushKV("start_height", start_height);
     response.pushKV("stop_height", result.last_scanned_height
                                        ? *result.last_scanned_height
                                        : UniValue());
     return response;
 }
 
 class DescribeWalletAddressVisitor : public boost::static_visitor<UniValue> {
 public:
     CWallet *const pwallet;
 
     void ProcessSubScript(const CScript &subscript, UniValue &obj,
                           bool include_addresses = false) const {
         // Always present: script type and redeemscript
         std::vector<std::vector<uint8_t>> solutions_data;
         txnouttype which_type = Solver(subscript, solutions_data);
         obj.pushKV("script", GetTxnOutputType(which_type));
         obj.pushKV("hex", HexStr(subscript.begin(), subscript.end()));
 
         CTxDestination embedded;
         UniValue a(UniValue::VARR);
         if (ExtractDestination(subscript, embedded)) {
             // Only when the script corresponds to an address.
             UniValue subobj(UniValue::VOBJ);
             UniValue detail = DescribeAddress(embedded);
             subobj.pushKVs(detail);
             UniValue wallet_detail = boost::apply_visitor(*this, embedded);
             subobj.pushKVs(wallet_detail);
             subobj.pushKV("address", EncodeDestination(embedded, GetConfig()));
             subobj.pushKV("scriptPubKey",
                           HexStr(subscript.begin(), subscript.end()));
             // Always report the pubkey at the top level, so that
             // `getnewaddress()['pubkey']` always works.
             if (subobj.exists("pubkey")) {
                 obj.pushKV("pubkey", subobj["pubkey"]);
             }
             obj.pushKV("embedded", std::move(subobj));
             if (include_addresses) {
                 a.push_back(EncodeDestination(embedded, GetConfig()));
             }
         } else if (which_type == TX_MULTISIG) {
             // Also report some information on multisig scripts (which do not
             // have a corresponding address).
             // TODO: abstract out the common functionality between this logic
             // and ExtractDestinations.
             obj.pushKV("sigsrequired", solutions_data[0][0]);
             UniValue pubkeys(UniValue::VARR);
             for (size_t i = 1; i < solutions_data.size() - 1; ++i) {
                 CPubKey key(solutions_data[i].begin(), solutions_data[i].end());
                 if (include_addresses) {
                     a.push_back(EncodeDestination(key.GetID(), GetConfig()));
                 }
                 pubkeys.push_back(HexStr(key.begin(), key.end()));
             }
             obj.pushKV("pubkeys", std::move(pubkeys));
         }
 
         // The "addresses" field is confusing because it refers to public keys
         // using their P2PKH address. For that reason, only add the 'addresses'
         // field when needed for backward compatibility. New applications can
         // use the 'pubkeys' field for inspecting multisig participants.
         if (include_addresses) {
             obj.pushKV("addresses", std::move(a));
         }
     }
 
     explicit DescribeWalletAddressVisitor(CWallet *_pwallet)
         : pwallet(_pwallet) {}
 
     UniValue operator()(const CNoDestination &dest) const {
         return UniValue(UniValue::VOBJ);
     }
 
     UniValue operator()(const CKeyID &keyID) const {
         UniValue obj(UniValue::VOBJ);
         CPubKey vchPubKey;
         if (pwallet && pwallet->GetPubKey(keyID, vchPubKey)) {
             obj.pushKV("pubkey", HexStr(vchPubKey));
             obj.pushKV("iscompressed", vchPubKey.IsCompressed());
         }
         return obj;
     }
 
     UniValue operator()(const CScriptID &scriptID) const {
         UniValue obj(UniValue::VOBJ);
         CScript subscript;
         if (pwallet && pwallet->GetCScript(scriptID, subscript)) {
             ProcessSubScript(subscript, obj, true);
         }
         return obj;
     }
 };
 
 static UniValue DescribeWalletAddress(CWallet *pwallet,
                                       const CTxDestination &dest) {
     UniValue ret(UniValue::VOBJ);
     UniValue detail = DescribeAddress(dest);
     ret.pushKVs(detail);
     ret.pushKVs(
         boost::apply_visitor(DescribeWalletAddressVisitor(pwallet), dest));
     return ret;
 }
 
 /** Convert CAddressBookData to JSON record.  */
 static UniValue AddressBookDataToJSON(const CAddressBookData &data,
                                       const bool verbose) {
     UniValue ret(UniValue::VOBJ);
     if (verbose) {
         ret.pushKV("name", data.name);
     }
     ret.pushKV("purpose", data.purpose);
     return ret;
 }
 
 UniValue getaddressinfo(const Config &config, const JSONRPCRequest &request) {
     std::shared_ptr<CWallet> const wallet = GetWalletForJSONRPCRequest(request);
     CWallet *const pwallet = wallet.get();
 
     if (!EnsureWalletIsAvailable(pwallet, request.fHelp)) {
         return NullUniValue;
     }
 
     if (request.fHelp || request.params.size() != 1) {
         throw std::runtime_error(RPCHelpMan{
             "getaddressinfo",
             "\nReturn information about the given bitcoin address. Some "
             "information requires the address\n"
             "to be in the wallet.\n",
             {
-                {"address", RPCArg::Type::STR, /* opt */ false,
-                 /* default_val */ "",
+                {"address", RPCArg::Type::STR, RPCArg::Optional::NO,
                  "The bitcoin address to get the information of."},
             },
             RPCResult{
                 "{\n"
                 "  \"address\" : \"address\",        (string) The bitcoin "
                 "address validated\n"
                 "  \"scriptPubKey\" : \"hex\",       (string) The hex-encoded "
                 "scriptPubKey generated by the address\n"
                 "  \"ismine\" : true|false,        (boolean) If the address is "
                 "yours or not\n"
                 "  \"iswatchonly\" : true|false,   (boolean) If the address is "
                 "watchonly\n"
                 "  \"solvable\" : true|false,      (boolean) Whether we know "
                 "how to spend coins sent to this address, ignoring the "
                 "possible lack of private keys\n"
                 "  \"desc\" : \"desc\",            (string, optional) A "
                 "descriptor for spending coins sent to this address (only when "
                 "solvable)\n"
                 "  \"isscript\" : true|false,      (boolean) If the key is a "
                 "script\n"
                 "  \"ischange\" : true|false,      (boolean) If the address "
                 "was used for change output\n"
                 "  \"script\" : \"type\"             (string, optional) The "
                 "output script type. Only if \"isscript\" is true and the "
                 "redeemscript is known. Possible types: nonstandard, pubkey, "
                 "pubkeyhash, scripthash, multisig, nulldata\n"
                 "  \"hex\" : \"hex\",                (string, optional) The "
                 "redeemscript for the p2sh address\n"
                 "  \"pubkeys\"                     (string, optional) Array of "
                 "pubkeys associated with the known redeemscript (only if "
                 "\"script\" is \"multisig\")\n"
                 "    [\n"
                 "      \"pubkey\"\n"
                 "      ,...\n"
                 "    ]\n"
                 "  \"sigsrequired\" : xxxxx        (numeric, optional) Number "
                 "of signatures required to spend multisig output (only if "
                 "\"script\" is \"multisig\")\n"
                 "  \"pubkey\" : \"publickeyhex\",    (string, optional) The "
                 "hex value of the raw public key, for single-key addresses "
                 "(possibly embedded in P2SH or P2WSH)\n"
                 "  \"embedded\" : {...},           (object, optional) "
                 "Information about the address embedded in P2SH or P2WSH, if "
                 "relevant and known. It includes all getaddressinfo output "
                 "fields for the embedded address, excluding metadata "
                 "(\"timestamp\", \"hdkeypath\", \"hdseedid\") and relation to "
                 "the wallet (\"ismine\", \"iswatchonly\").\n"
                 "  \"iscompressed\" : true|false,  (boolean) If the address is "
                 "compressed\n"
                 "  \"label\" :  \"label\"         (string) The label "
                 "associated with the address, \"\" is the default label\n"
                 "  \"timestamp\" : timestamp,      (number, optional) The "
                 "creation time of the key if available in seconds since epoch "
                 "(Jan 1 1970 GMT)\n"
                 "  \"hdkeypath\" : \"keypath\"       (string, optional) The HD "
                 "keypath if the key is HD and available\n"
                 "  \"hdseedid\" : \"<hash160>\"      (string, optional) The "
                 "Hash160 of the HD seed\n"
                 "  \"hdmasterkeyid\" : \"<hash160>\" (string, optional) alias "
                 "for hdseedid maintained for backwards compatibility. Will be "
                 "removed in V0.21.\n"
                 "  \"labels\"                      (object) Array of labels "
                 "associated with the address.\n"
                 "    [\n"
                 "      { (json object of label data)\n"
                 "        \"name\": \"labelname\" (string) The label\n"
                 "        \"purpose\": \"string\" (string) Purpose of address "
                 "(\"send\" for sending address, \"receive\" for receiving "
                 "address)\n"
                 "      },...\n"
                 "    ]\n"
                 "}\n"},
             RPCExamples{
                 HelpExampleCli("getaddressinfo",
                                "\"1PSSGeFHDnKNxiEyFrD1wcEaHr9hrQDDWc\"") +
                 HelpExampleRpc("getaddressinfo",
                                "\"1PSSGeFHDnKNxiEyFrD1wcEaHr9hrQDDWc\"")},
         }
                                      .ToString());
     }
 
     LOCK(pwallet->cs_wallet);
 
     UniValue ret(UniValue::VOBJ);
     CTxDestination dest =
         DecodeDestination(request.params[0].get_str(), config.GetChainParams());
 
     // Make sure the destination is valid
     if (!IsValidDestination(dest)) {
         throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Invalid address");
     }
 
     std::string currentAddress = EncodeDestination(dest, config);
     ret.pushKV("address", currentAddress);
 
     CScript scriptPubKey = GetScriptForDestination(dest);
     ret.pushKV("scriptPubKey",
                HexStr(scriptPubKey.begin(), scriptPubKey.end()));
 
     isminetype mine = IsMine(*pwallet, dest);
     ret.pushKV("ismine", bool(mine & ISMINE_SPENDABLE));
     bool solvable = IsSolvable(*pwallet, scriptPubKey);
     ret.pushKV("solvable", solvable);
     if (solvable) {
         ret.pushKV("desc", InferDescriptor(scriptPubKey, *pwallet)->ToString());
     }
     ret.pushKV("iswatchonly", bool(mine & ISMINE_WATCH_ONLY));
     UniValue detail = DescribeWalletAddress(pwallet, dest);
     ret.pushKVs(detail);
     if (pwallet->mapAddressBook.count(dest)) {
         ret.pushKV("label", pwallet->mapAddressBook[dest].name);
     }
     ret.pushKV("ischange", pwallet->IsChange(scriptPubKey));
     const CKeyMetadata *meta = nullptr;
     CKeyID key_id = GetKeyForDestination(*pwallet, dest);
     if (!key_id.IsNull()) {
         auto it = pwallet->mapKeyMetadata.find(key_id);
         if (it != pwallet->mapKeyMetadata.end()) {
             meta = &it->second;
         }
     }
     if (!meta) {
         auto it = pwallet->m_script_metadata.find(CScriptID(scriptPubKey));
         if (it != pwallet->m_script_metadata.end()) {
             meta = &it->second;
         }
     }
     if (meta) {
         ret.pushKV("timestamp", meta->nCreateTime);
         if (!meta->hdKeypath.empty()) {
             ret.pushKV("hdkeypath", meta->hdKeypath);
             ret.pushKV("hdseedid", meta->hd_seed_id.GetHex());
             ret.pushKV("hdmasterkeyid", meta->hd_seed_id.GetHex());
         }
     }
 
     // Currently only one label can be associated with an address, return an
     // array so the API remains stable if we allow multiple labels to be
     // associated with an address.
     UniValue labels(UniValue::VARR);
     std::map<CTxDestination, CAddressBookData>::iterator mi =
         pwallet->mapAddressBook.find(dest);
     if (mi != pwallet->mapAddressBook.end()) {
         labels.push_back(AddressBookDataToJSON(mi->second, true));
     }
     ret.pushKV("labels", std::move(labels));
 
     return ret;
 }
 
 UniValue getaddressesbylabel(const Config &config,
                              const JSONRPCRequest &request) {
     std::shared_ptr<CWallet> const wallet = GetWalletForJSONRPCRequest(request);
     CWallet *const pwallet = wallet.get();
     if (!EnsureWalletIsAvailable(pwallet, request.fHelp)) {
         return NullUniValue;
     }
 
     if (request.fHelp || request.params.size() != 1) {
         throw std::runtime_error(RPCHelpMan{
             "getaddressesbylabel",
             "\nReturns the list of addresses assigned the specified "
             "label.\n",
             {
-                {"label", RPCArg::Type::STR, /* opt */ false,
-                 /* default_val */ "", "The label."},
+                {"label", RPCArg::Type::STR, RPCArg::Optional::NO,
+                 "The label."},
             },
             RPCResult{"{ (json object with addresses as keys)\n"
                       "  \"address\": { (json object with information about "
                       "address)\n"
                       "    \"purpose\": \"string\" (string)  Purpose of "
                       "address (\"send\" for sending address, \"receive\" for "
                       "receiving address)\n"
                       "  },...\n"
                       "}\n"},
             RPCExamples{HelpExampleCli("getaddressesbylabel", "\"tabby\"") +
                         HelpExampleRpc("getaddressesbylabel", "\"tabby\"")},
         }
                                      .ToString());
     }
 
     LOCK(pwallet->cs_wallet);
 
     std::string label = LabelFromValue(request.params[0]);
 
     // Find all addresses that have the given label
     UniValue ret(UniValue::VOBJ);
     std::set<std::string> addresses;
     for (const std::pair<const CTxDestination, CAddressBookData> &item :
          pwallet->mapAddressBook) {
         if (item.second.name == label) {
             std::string address = EncodeDestination(item.first, config);
             // CWallet::mapAddressBook is not expected to contain duplicate
             // address strings, but build a separate set as a precaution just in
             // case it does.
             bool unique = addresses.emplace(address).second;
             assert(unique);
             // UniValue::pushKV checks if the key exists in O(N)
             // and since duplicate addresses are unexpected (checked with
             // std::set in O(log(N))), UniValue::__pushKV is used instead,
             // which currently is O(1).
             ret.__pushKV(address, AddressBookDataToJSON(item.second, false));
         }
     }
 
     if (ret.empty()) {
         throw JSONRPCError(RPC_WALLET_INVALID_LABEL_NAME,
                            std::string("No addresses with label " + label));
     }
 
     return ret;
 }
 
 UniValue listlabels(const Config &config, const JSONRPCRequest &request) {
     std::shared_ptr<CWallet> const wallet = GetWalletForJSONRPCRequest(request);
     CWallet *const pwallet = wallet.get();
     if (!EnsureWalletIsAvailable(pwallet, request.fHelp)) {
         return NullUniValue;
     }
 
     if (request.fHelp || request.params.size() > 1) {
         throw std::runtime_error(RPCHelpMan{
             "listlabels",
             "\nReturns the list of all labels, or labels that are "
             "assigned to addresses with a specific purpose.\n",
             {
-                {"purpose", RPCArg::Type::STR, /* opt */ true,
-                 /* default_val */ "null",
+                {"purpose", RPCArg::Type::STR,
+                 RPCArg::Optional::OMITTED_NAMED_ARG,
                  "Address purpose to list labels for ('send','receive'). An "
                  "empty string is the same as not providing this argument."},
             },
             RPCResult{"[               (json array of string)\n"
                       "  \"label\",      (string) Label name\n"
                       "  ...\n"
                       "]\n"},
             RPCExamples{"\nList all labels\n" +
                         HelpExampleCli("listlabels", "") +
                         "\nList labels that have receiving addresses\n" +
                         HelpExampleCli("listlabels", "receive") +
                         "\nList labels that have sending addresses\n" +
                         HelpExampleCli("listlabels", "send") +
                         "\nAs a JSON-RPC call\n" +
                         HelpExampleRpc("listlabels", "receive")},
         }
                                      .ToString());
     }
 
     LOCK(pwallet->cs_wallet);
 
     std::string purpose;
     if (!request.params[0].isNull()) {
         purpose = request.params[0].get_str();
     }
 
     // Add to a set to sort by label name, then insert into Univalue array
     std::set<std::string> label_set;
     for (const std::pair<const CTxDestination, CAddressBookData> &entry :
          pwallet->mapAddressBook) {
         if (purpose.empty() || entry.second.purpose == purpose) {
             label_set.insert(entry.second.name);
         }
     }
 
     UniValue ret(UniValue::VARR);
     for (const std::string &name : label_set) {
         ret.push_back(name);
     }
 
     return ret;
 }
 
 static UniValue sethdseed(const Config &config, const JSONRPCRequest &request) {
     std::shared_ptr<CWallet> const wallet = GetWalletForJSONRPCRequest(request);
     CWallet *const pwallet = wallet.get();
 
     if (!EnsureWalletIsAvailable(pwallet, request.fHelp)) {
         return NullUniValue;
     }
 
     if (request.fHelp || request.params.size() > 2) {
         throw std::runtime_error(RPCHelpMan{
             "sethdseed",
             "\nSet or generate a new HD wallet seed. Non-HD wallets will not "
             "be upgraded to being a HD wallet. Wallets that are already\n"
             "HD will have a new HD seed set so that new keys added to the "
             "keypool will be derived from this new seed.\n"
             "\nNote that you will need to MAKE A NEW BACKUP of your wallet "
             "after setting the HD wallet seed.\n" +
                 HelpRequiringPassphrase(pwallet) + "\n",
             {
-                {"newkeypool", RPCArg::Type::BOOL, /* opt */ true,
-                 /* default_val */ "true",
+                {"newkeypool", RPCArg::Type::BOOL, /* default */ "true",
                  "Whether to flush old unused addresses, including change "
                  "addresses, from the keypool and regenerate it.\n"
                  "                             If true, the next address from "
                  "getnewaddress and change address from getrawchangeaddress "
                  "will be from this new seed.\n"
                  "                             If false, addresses (including "
                  "change addresses if the wallet already had HD Chain Split "
                  "enabled) from the existing\n"
                  "                             keypool will be used until it "
                  "has been depleted."},
-                {"seed", RPCArg::Type::STR, /* opt */ true,
-                 /* default_val */ "random seed",
+                {"seed", RPCArg::Type::STR, /* default */ "random seed",
                  "The WIF private key to use as the new HD seed.\n"
                  "                             The seed value can be retrieved "
                  "using the dumpwallet command. It is the private key marked "
                  "hdseed=1"},
             },
             RPCResults{},
             RPCExamples{HelpExampleCli("sethdseed", "") +
                         HelpExampleCli("sethdseed", "false") +
                         HelpExampleCli("sethdseed", "true \"wifkey\"") +
                         HelpExampleRpc("sethdseed", "true, \"wifkey\"")},
         }
                                      .ToString());
     }
 
     if (pwallet->chain().isInitialBlockDownload()) {
         throw JSONRPCError(
             RPC_CLIENT_IN_INITIAL_DOWNLOAD,
             "Cannot set a new HD seed while still in Initial Block Download");
     }
 
     if (pwallet->IsWalletFlagSet(WALLET_FLAG_DISABLE_PRIVATE_KEYS)) {
         throw JSONRPCError(
             RPC_WALLET_ERROR,
             "Cannot set a HD seed to a wallet with private keys disabled");
     }
 
     auto locked_chain = pwallet->chain().lock();
     LOCK(pwallet->cs_wallet);
 
     // Do not do anything to non-HD wallets
     if (!pwallet->CanSupportFeature(FEATURE_HD)) {
         throw JSONRPCError(
             RPC_WALLET_ERROR,
             "Cannot set a HD seed on a non-HD wallet. Start with "
             "-upgradewallet in order to upgrade a non-HD wallet to HD");
     }
 
     EnsureWalletIsUnlocked(pwallet);
 
     bool flush_key_pool = true;
     if (!request.params[0].isNull()) {
         flush_key_pool = request.params[0].get_bool();
     }
 
     CPubKey master_pub_key;
     if (request.params[1].isNull()) {
         master_pub_key = pwallet->GenerateNewSeed();
     } else {
         CKey key = DecodeSecret(request.params[1].get_str());
         if (!key.IsValid()) {
             throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY,
                                "Invalid private key");
         }
 
         if (HaveKey(*pwallet, key)) {
             throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY,
                                "Already have this key (either as an HD seed or "
                                "as a loose private key)");
         }
 
         master_pub_key = pwallet->DeriveNewSeed(key);
     }
 
     pwallet->SetHDSeed(master_pub_key);
     if (flush_key_pool) {
         pwallet->NewKeyPool();
     }
 
     return NullUniValue;
 }
 
 static UniValue walletprocesspsbt(const Config &config,
                                   const JSONRPCRequest &request) {
     std::shared_ptr<CWallet> const wallet = GetWalletForJSONRPCRequest(request);
     CWallet *const pwallet = wallet.get();
 
     if (!EnsureWalletIsAvailable(pwallet, request.fHelp)) {
         return NullUniValue;
     }
 
     if (request.fHelp || request.params.size() < 1 ||
         request.params.size() > 4) {
         throw std::runtime_error(RPCHelpMan{
             "walletprocesspsbt",
             "\nUpdate a PSBT with input information from our wallet and then "
             "sign inputs that we can sign for." +
                 HelpRequiringPassphrase(pwallet) + "\n",
             {
-                {"psbt", RPCArg::Type::STR, /* opt */ false,
-                 /* default_val */ "", "The transaction base64 string"},
-                {"sign", RPCArg::Type::BOOL, /* opt */ true,
-                 /* default_val */ "true",
+                {"psbt", RPCArg::Type::STR, RPCArg::Optional::NO,
+                 "The transaction base64 string"},
+                {"sign", RPCArg::Type::BOOL, /* default */ "true",
                  "Also sign the transaction when updating"},
-                {"sighashtype", RPCArg::Type::STR, /* opt */ true,
-                 /* default_val */ "ALL|FORKID",
+                {"sighashtype", RPCArg::Type::STR, /* default */ "ALL|FORKID",
                  "The signature hash type to sign with if not specified by "
                  "the PSBT. Must be one of\n"
                  "       \"ALL|FORKID\"\n"
                  "       \"NONE|FORKID\"\n"
                  "       \"SINGLE|FORKID\"\n"
                  "       \"ALL|FORKID|ANYONECANPAY\"\n"
                  "       \"NONE|FORKID|ANYONECANPAY\"\n"
                  "       \"SINGLE|FORKID|ANYONECANPAY\""},
-                {"bip32derivs", RPCArg::Type::BOOL, /* opt */ true,
-                 /* default_val */ "false",
+                {"bip32derivs", RPCArg::Type::BOOL, /* default */ "false",
                  "If true, includes the BIP 32 derivation paths for public "
                  "keys if we know them"},
             },
             RPCResult{"{\n"
                       "  \"psbt\" : \"value\",          (string) The "
                       "base64-encoded partially signed transaction\n"
                       "  \"complete\" : true|false,   (boolean) If the "
                       "transaction has a complete set of signatures\n"
                       "  ]\n"
                       "}\n"},
             RPCExamples{HelpExampleCli("walletprocesspsbt", "\"psbt\"")},
         }
                                      .ToString());
     }
 
     RPCTypeCheck(request.params,
                  {UniValue::VSTR, UniValue::VBOOL, UniValue::VSTR});
 
     // Unserialize the transaction
     PartiallySignedTransaction psbtx;
     std::string error;
     if (!DecodeBase64PSBT(psbtx, request.params[0].get_str(), error)) {
         throw JSONRPCError(RPC_DESERIALIZATION_ERROR,
                            strprintf("TX decode failed %s", error));
     }
 
     // Get the sighash type
     SigHashType nHashType = ParseSighashString(request.params[2]);
     if (!nHashType.hasForkId()) {
         throw JSONRPCError(RPC_INVALID_PARAMETER,
                            "Signature must use SIGHASH_FORKID");
     }
 
     // Fill transaction with our data and also sign
     bool sign =
         request.params[1].isNull() ? true : request.params[1].get_bool();
     bool bip32derivs =
         request.params[3].isNull() ? false : request.params[3].get_bool();
     bool complete = true;
     const TransactionError err =
         FillPSBT(pwallet, psbtx, complete, nHashType, sign, bip32derivs);
     if (err != TransactionError::OK) {
         throw JSONRPCTransactionError(err);
     }
 
     UniValue result(UniValue::VOBJ);
     CDataStream ssTx(SER_NETWORK, PROTOCOL_VERSION);
     ssTx << psbtx;
     result.pushKV("psbt", EncodeBase64(ssTx.str()));
     result.pushKV("complete", complete);
 
     return result;
 }
 
 static UniValue walletcreatefundedpsbt(const Config &config,
                                        const JSONRPCRequest &request) {
     std::shared_ptr<CWallet> const wallet = GetWalletForJSONRPCRequest(request);
     CWallet *const pwallet = wallet.get();
 
     if (!EnsureWalletIsAvailable(pwallet, request.fHelp)) {
         return NullUniValue;
     }
 
     if (request.fHelp || request.params.size() < 2 ||
         request.params.size() > 5) {
         throw std::runtime_error(RPCHelpMan{
             "walletcreatefundedpsbt",
             "\nCreates and funds a transaction in the Partially Signed "
             "Transaction format. Inputs will be added if supplied inputs are "
             "not enough\n"
             "Implements the Creator and Updater roles.\n",
             {
                 {
                     "inputs",
                     RPCArg::Type::ARR,
-                    /* opt */ false,
-                    /* default_val */ "",
+                    RPCArg::Optional::NO,
                     "A json array of json objects",
                     {
                         {
                             "",
                             RPCArg::Type::OBJ,
-                            /* opt */ false,
-                            /* default_val */ "",
+                            RPCArg::Optional::OMITTED,
                             "",
                             {
                                 {"txid", RPCArg::Type::STR_HEX,
-                                 /* opt */ false, /* default_val */ "",
-                                 "The transaction id"},
-                                {"vout", RPCArg::Type::NUM, /* opt */ false,
-                                 /* default_val */ "", "The output number"},
+                                 RPCArg::Optional::NO, "The transaction id"},
+                                {"vout", RPCArg::Type::NUM,
+                                 RPCArg::Optional::NO, "The output number"},
                                 {"sequence", RPCArg::Type::NUM,
-                                 /* opt */ false, /* default_val */ "",
-                                 "The sequence number"},
+                                 RPCArg::Optional::NO, "The sequence number"},
                             },
                         },
                     },
                 },
                 {
                     "outputs",
                     RPCArg::Type::ARR,
-                    /* opt */ false,
-                    /* default_val */ "",
+                    RPCArg::Optional::NO,
                     "a json array with outputs (key-value pairs).\n"
                     "For compatibility reasons, a dictionary, which holds "
                     "the key-value pairs directly, is also\n"
                     "                             accepted as second "
                     "parameter.",
                     {
                         {
                             "",
                             RPCArg::Type::OBJ,
-                            /* opt */ true,
-                            /* default_val */ "",
+                            RPCArg::Optional::OMITTED,
                             "",
                             {
                                 {"address", RPCArg::Type::AMOUNT,
-                                 /* opt */ false, /* default_val */ "",
+                                 RPCArg::Optional::NO,
                                  "A key-value pair. The key (string) is the "
                                  "bitcoin address, the value (float or string) "
                                  "is the amount in " +
                                      CURRENCY_UNIT + ""},
                             },
                         },
                         {
                             "",
                             RPCArg::Type::OBJ,
-                            /* opt */ true,
-                            /* default_val */ "",
+                            RPCArg::Optional::OMITTED,
                             "",
                             {
-                                {"data", RPCArg::Type::STR_HEX, /* opt */ false,
-                                 /* default_val */ "",
+                                {"data", RPCArg::Type::STR_HEX,
+                                 RPCArg::Optional::NO,
                                  "A key-value pair. The key must be \"data\", "
                                  "the value is hex-encoded data"},
                             },
                         },
                     },
                 },
-                {"locktime", RPCArg::Type::NUM, /* opt */ true,
-                 /* default_val */ "0",
+                {"locktime", RPCArg::Type::NUM, /* default */ "0",
                  "Raw locktime. Non-0 value also locktime-activates inputs\n"
                  "                             Allows this transaction to "
                  "be replaced by a transaction with higher fees. If provided, "
                  "it is an error if explicit sequence numbers are "
                  "incompatible."},
                 {"options",
                  RPCArg::Type::OBJ,
-                 /* opt */ true,
-                 /* default_val */ "null",
+                 RPCArg::Optional::OMITTED_NAMED_ARG,
                  "",
                  {
                      {"changeAddress", RPCArg::Type::STR_HEX,
-                      /* opt */ true, /* default_val */ "pool address",
+                      /* default */ "pool address",
                       "The bitcoin address to receive the change"},
-                     {"changePosition", RPCArg::Type::NUM, /* opt */ true,
-                      /* default_val */ "random",
-                      "The index of the change output"},
-                     {"includeWatching", RPCArg::Type::BOOL, /* opt */ true,
-                      /* default_val */ "false",
+                     {"changePosition", RPCArg::Type::NUM,
+                      /* default */ "random", "The index of the change output"},
+                     {"includeWatching", RPCArg::Type::BOOL,
+                      /* default */ "false",
                       "Also select inputs which are watch only"},
-                     {"lockUnspents", RPCArg::Type::BOOL, /* opt */ true,
-                      /* default_val */ "false",
+                     {"lockUnspents", RPCArg::Type::BOOL, /* default */ "false",
                       "Lock selected unspent outputs"},
-                     {"feeRate", RPCArg::Type::AMOUNT, /* opt */ true,
-                      /* default_val */
+                     {"feeRate", RPCArg::Type::AMOUNT, /* default */
                       "not set: makes wallet determine the fee",
                       "Set a specific fee rate in " + CURRENCY_UNIT + "/kB"},
                      {
                          "subtractFeeFromOutputs",
                          RPCArg::Type::ARR,
-                         /* opt */ true,
-                         /* default_val */ "empty array",
+                         /* default */ "empty array",
                          "A json array of integers.\n"
                          "                              The fee will be "
                          "equally deducted from the amount of each specified "
                          "output.\n"
                          "                              Those recipients will "
                          "receive less bitcoins than you enter in their "
                          "corresponding amount field.\n"
                          "                              If no outputs are "
                          "specified here, the sender pays the fee.",
                          {
-                             {"vout_index", RPCArg::Type::NUM, /* opt */ true,
-                              /* default_val */ "",
+                             {"vout_index", RPCArg::Type::NUM,
+                              RPCArg::Optional::OMITTED,
                               "The zero-based output index, before a change "
                               "output is added."},
                          },
                      },
                  },
                  "options"},
-                {"bip32derivs", RPCArg::Type::BOOL, /* opt */ true,
-                 /* default_val */ "false",
+                {"bip32derivs", RPCArg::Type::BOOL, /* default */ "false",
                  "If true, includes the BIP 32 derivation paths for public "
                  "keys if we know them"},
             },
             RPCResult{"{\n"
                       "  \"psbt\": \"value\",        (string)  The resulting "
                       "raw transaction (base64-encoded string)\n"
                       "  \"fee\":       n,         (numeric) Fee in " +
                       CURRENCY_UNIT +
                       " the resulting transaction pays\n"
                       "  \"changepos\": n          (numeric) The position of "
                       "the added change output, or -1\n"
                       "}\n"},
             RPCExamples{"\nCreate a transaction with no inputs\n" +
                         HelpExampleCli(
                             "walletcreatefundedpsbt",
                             "\"[{\\\"txid\\\":\\\"myid\\\",\\\"vout\\\":0}]\" "
                             "\"[{\\\"data\\\":\\\"00010203\\\"}]\"")},
         }
                                      .ToString());
     }
 
     RPCTypeCheck(request.params,
                  {UniValue::VARR,
                   UniValueType(), // ARR or OBJ, checked later
                   UniValue::VNUM, UniValue::VOBJ},
                  true);
 
     Amount fee;
     int change_position;
     CMutableTransaction rawTx =
         ConstructTransaction(config.GetChainParams(), request.params[0],
                              request.params[1], request.params[2]);
     FundTransaction(pwallet, rawTx, fee, change_position, request.params[3]);
 
     // Make a blank psbt
     PartiallySignedTransaction psbtx(rawTx);
 
     // Fill transaction with out data but don't sign
     bool bip32derivs =
         request.params[4].isNull() ? false : request.params[4].get_bool();
     bool complete = true;
     const TransactionError err =
         FillPSBT(pwallet, psbtx, complete, SigHashType().withForkId(), false,
                  bip32derivs);
     if (err != TransactionError::OK) {
         throw JSONRPCTransactionError(err);
     }
 
     // Serialize the PSBT
     CDataStream ssTx(SER_NETWORK, PROTOCOL_VERSION);
     ssTx << psbtx;
 
     UniValue result(UniValue::VOBJ);
     result.pushKV("psbt", EncodeBase64(ssTx.str()));
     result.pushKV("fee", ValueFromAmount(fee));
     result.pushKV("changepos", change_position);
     return result;
 }
 
 // clang-format off
 static const CRPCCommand commands[] = {
     //  category            name                            actor (function)              argNames
     //  ------------------- ------------------------        ----------------------        ----------
     { "generating",         "generate",                     generate,                     {"nblocks","maxtries"} },
     { "rawtransactions",    "fundrawtransaction",           fundrawtransaction,           {"hexstring","options"} },
     { "wallet",             "abandontransaction",           abandontransaction,           {"txid"} },
     { "wallet",             "addmultisigaddress",           addmultisigaddress,           {"nrequired","keys","label"} },
     { "wallet",             "backupwallet",                 backupwallet,                 {"destination"} },
     { "wallet",             "createwallet",                 createwallet,                 {"wallet_name", "disable_private_keys", "blank"} },
     { "wallet",             "encryptwallet",                encryptwallet,                {"passphrase"} },
     { "wallet",             "getaddressesbylabel",          getaddressesbylabel,          {"label"} },
     { "wallet",             "getaddressinfo",               getaddressinfo,               {"address"} },
     { "wallet",             "getbalance",                   getbalance,                   {"dummy","minconf","include_watchonly"} },
     { "wallet",             "getnewaddress",                getnewaddress,                {"label", "address_type"} },
     { "wallet",             "getrawchangeaddress",          getrawchangeaddress,          {"address_type"} },
     { "wallet",             "getreceivedbyaddress",         getreceivedbyaddress,         {"address","minconf"} },
     { "wallet",             "getreceivedbylabel",           getreceivedbylabel,           {"label","minconf"} },
     { "wallet",             "gettransaction",               gettransaction,               {"txid","include_watchonly"} },
     { "wallet",             "getunconfirmedbalance",        getunconfirmedbalance,        {} },
     { "wallet",             "getwalletinfo",                getwalletinfo,                {} },
     { "wallet",             "keypoolrefill",                keypoolrefill,                {"newsize"} },
     { "wallet",             "listaddressgroupings",         listaddressgroupings,         {} },
     { "wallet",             "listlabels",                   listlabels,                   {"purpose"} },
     { "wallet",             "listlockunspent",              listlockunspent,              {} },
     { "wallet",             "listreceivedbyaddress",        listreceivedbyaddress,        {"minconf","include_empty","include_watchonly","address_filter"} },
     { "wallet",             "listreceivedbylabel",          listreceivedbylabel,          {"minconf","include_empty","include_watchonly"} },
     { "wallet",             "listsinceblock",               listsinceblock,               {"blockhash","target_confirmations","include_watchonly","include_removed"} },
     { "wallet",             "listtransactions",             listtransactions,             {"label|dummy","count","skip","include_watchonly"} },
     { "wallet",             "listunspent",                  listunspent,                  {"minconf","maxconf","addresses","include_unsafe","query_options"} },
     { "wallet",             "listwalletdir",                listwalletdir,                {} },
     { "wallet",             "listwallets",                  listwallets,                  {} },
     { "wallet",             "loadwallet",                   loadwallet,                   {"filename"} },
     { "wallet",             "lockunspent",                  lockunspent,                  {"unlock","transactions"} },
     { "wallet",             "rescanblockchain",             rescanblockchain,             {"start_height", "stop_height"} },
     { "wallet",             "sendmany",                     sendmany,                     {"dummy","amounts","minconf","comment","subtractfeefrom"} },
     { "wallet",             "sendtoaddress",                sendtoaddress,                {"address","amount","comment","comment_to","subtractfeefromamount"} },
     { "wallet",             "sethdseed",                    sethdseed,                    {"newkeypool","seed"} },
     { "wallet",             "setlabel",                     setlabel,                     {"address","label"} },
     { "wallet",             "settxfee",                     settxfee,                     {"amount"} },
     { "wallet",             "signmessage",                  signmessage,                  {"address","message"} },
     { "wallet",             "signrawtransactionwithwallet", signrawtransactionwithwallet, {"hextring","prevtxs","sighashtype"} },
     { "wallet",             "unloadwallet",                 unloadwallet,                 {"wallet_name"} },
     { "wallet",             "walletcreatefundedpsbt",       walletcreatefundedpsbt,       {"inputs","outputs","locktime","options","bip32derivs"} },
     { "wallet",             "walletlock",                   walletlock,                   {} },
     { "wallet",             "walletpassphrase",             walletpassphrase,             {"passphrase","timeout"} },
     { "wallet",             "walletpassphrasechange",       walletpassphrasechange,       {"oldpassphrase","newpassphrase"} },
     { "wallet",             "walletprocesspsbt",            walletprocesspsbt,            {"psbt","sign","sighashtype","bip32derivs"} },
 };
 // clang-format on
 
 void RegisterWalletRPCCommands(
     interfaces::Chain &chain,
     std::vector<std::unique_ptr<interfaces::Handler>> &handlers) {
     for (unsigned int vcidx = 0; vcidx < ARRAYLEN(commands); vcidx++) {
         handlers.emplace_back(chain.handleRpc(commands[vcidx]));
     }
 }