diff --git a/lib/bcoin/http/rpc.js b/lib/bcoin/http/rpc.js
index 08d43c96..7348d108 100644
--- a/lib/bcoin/http/rpc.js
+++ b/lib/bcoin/http/rpc.js
@@ -268,7 +268,7 @@ RPC.prototype.getinfo = function getinfo(args, callback) {
   var self = this;
 
   if (args.help || args.length !== 0)
-    return callback(new Error('getinfo'));
+    return callback(new RPCError('getinfo'));
 
   this.wallet.getBalance(function(err, balance) {
     if (err)
@@ -307,7 +307,7 @@ RPC.prototype.help = function help(args, callback) {
 
 RPC.prototype.stop = function stop(args, callback) {
   if (args.help || args.length !== 0)
-    return callback(new Error('stop'));
+    return callback(new RPCError('stop'));
 
   callback(null, 'Stopping.');
   this.node.close();
@@ -358,7 +358,7 @@ RPC.prototype.addnode = function addnode(args, callback) {
   var i, node, cmd, host, seed;
 
   if (args.help || args.length !== 2)
-    return callback(new Error('addnode "node" "add|remove|onetry"'));
+    return callback(new RPCError('addnode "node" "add|remove|onetry"'));
 
   node = String(args[0]);
   cmd = String(args[1]);
@@ -388,7 +388,7 @@ RPC.prototype.disconnectnode = function disconnectnode(args, callback) {
   var node, peer;
 
   if (args.help || args.length !== 1)
-    return callback(new Error('disconnectnode "node"'));
+    return callback(new RPCError('disconnectnode "node"'));
 
   node = String(args[0]);
   node = IP.normalize(node);
@@ -402,19 +402,19 @@ RPC.prototype.disconnectnode = function disconnectnode(args, callback) {
 
 RPC.prototype.getaddednodeinfo = function getaddednodeinfo(args, callback) {
   if (args.help || args.length < 1 || args.length > 2)
-    return callback(new Error('getaddednodeinfo dummy ( "node" )'));
+    return callback(new RPCError('getaddednodeinfo dummy ( "node" )'));
   callback(new Error('Not implemented.'));
 };
 
 RPC.prototype.getconnectioncount = function getconnectioncount(args, callback) {
   if (args.help || args.length !== 0)
-    return callback(new Error('getconnectioncount'));
+    return callback(new RPCError('getconnectioncount'));
   callback(null, this.pool.peers.all.length);
 };
 
 RPC.prototype.getnettotals = function getnettotals(args, callback) {
   if (args.help || args.length > 0)
-    return callback(new Error('getnettotals'));
+    return callback(new RPCError('getnettotals'));
 
   callback(null, {
     totalbytesrecv: 0,
@@ -438,7 +438,7 @@ RPC.prototype.getpeerinfo = function getpeerinfo(args, callback) {
   var i, peer;
 
   if (args.help || args.length !== 0)
-    return callback(new Error('getpeerinfo'));
+    return callback(new RPCError('getpeerinfo'));
 
   for (i = 0; i < this.pool.peers.all.length; i++) {
     peer = this.pool.peers.all[i];
@@ -474,7 +474,7 @@ RPC.prototype.ping = function ping(args, callback) {
   var i;
 
   if (args.help || args.length !== 0)
-    return callback(new Error('ping'));
+    return callback(new RPCError('ping'));
 
   for (i = 0; i < this.pool.peers.all.length; i++)
     this.pool.peers.all[i].sendPing();
@@ -488,7 +488,7 @@ RPC.prototype.setban = function setban(args, callback) {
   if (args.help
       || args.length < 2
       || (args[1] !== 'add' && args[1] !== 'remove')) {
-    return callback(new Error(
+    return callback(new RPCError(
       'setban "ip(/netmask)" "add|remove" (bantime) (absolute)'));
   }
 
@@ -514,7 +514,7 @@ RPC.prototype.listbanned = function listbanned(args, callback) {
   var i, banned, keys, host, time;
 
   if (args.help || args.length !== 0)
-    return callback(new Error('listbanned'));
+    return callback(new RPCError('listbanned'));
 
   banned = [];
   keys = Object.keys(this.pool.peers.misbehaving);
@@ -535,7 +535,7 @@ RPC.prototype.listbanned = function listbanned(args, callback) {
 
 RPC.prototype.clearbanned = function clearbanned(args, callback) {
   if (args.help || args.length !== 0)
-    return callback(new Error('clearbanned'));
+    return callback(new RPCError('clearbanned'));
 
   this.pool.peers.ignored = {};
   this.pool.peers.misbehaving = {};
@@ -617,7 +617,7 @@ RPC.prototype.getblockchaininfo = function getblockchaininfo(args, callback) {
   var self = this;
 
   if (args.help || args.length !== 0)
-    return callback(new Error('getblockchaininfo'));
+    return callback(new RPCError('getblockchaininfo'));
 
   this.chain.tip.getMedianTimeAsync(function(err, medianTime) {
     if (err)
@@ -674,14 +674,14 @@ RPC.prototype._getDifficulty = function getDifficulty(entry) {
 
 RPC.prototype.getbestblockhash = function getbestblockhash(args, callback) {
   if (args.help || args.length !== 0)
-    return callback(new Error('getbestblockhash'));
+    return callback(new RPCError('getbestblockhash'));
 
   callback(null, this.chain.tip.rhash);
 };
 
 RPC.prototype.getblockcount = function getblockcount(args, callback) {
   if (args.help || args.length !== 0)
-    return callback(new Error('getblockcount'));
+    return callback(new RPCError('getblockcount'));
 
   callback(null, this.chain.tip.height);
 };
@@ -691,7 +691,7 @@ RPC.prototype.getblock = function getblock(args, callback) {
   var hash, verbose;
 
   if (args.help || args.length < 1 || args.length > 2)
-    return callback(new Error('getblock "hash" ( verbose )'));
+    return callback(new RPCError('getblock "hash" ( verbose )'));
 
   hash = utils.revHex(String(args[0]));
 
@@ -705,7 +705,7 @@ RPC.prototype.getblock = function getblock(args, callback) {
       return callback(err);
 
     if (!entry)
-      return callback(new Error('Block not found'));
+      return callback(new RPCError('Block not found'));
 
     self.chain.db.getBlock(entry.hash, function(err, block) {
       if (err)
@@ -713,8 +713,8 @@ RPC.prototype.getblock = function getblock(args, callback) {
 
       if (!block) {
         if (self.chain.db.prune)
-          return callback(new Error('Block not available (pruned data)'));
-        return callback(new Error('Can\'t read block from disk'));
+          return callback(new RPCError('Block not available (pruned data)'));
+        return callback(new RPCError('Can\'t read block from disk'));
       }
 
       if (!verbose)
@@ -792,19 +792,19 @@ RPC.prototype.getblockhash = function getblockhash(args, callback) {
   var height;
 
   if (args.help || args.length !== 1)
-    return callback(new Error('getblockhash index'));
+    return callback(new RPCError('getblockhash index'));
 
   height = args[0];
 
   if (height < 0 || height > this.chain.height)
-    return callback(new Error('Block height out of range.'));
+    return callback(new RPCError('Block height out of range.'));
 
   this.chain.db.get(height, function(err, entry) {
     if (err)
       return callback(err);
 
     if (!entry)
-      return callback(new Error('Not found.'));
+      return callback(new RPCError('Not found.'));
 
     return callback(null, entry.rhash);
   });
@@ -815,7 +815,7 @@ RPC.prototype.getblockheader = function getblockheader(args, callback) {
   var hash, verbose;
 
   if (args.help || args.length < 1 || args.length > 2)
-    return callback(new Error('getblockheader "hash" ( verbose )'));
+    return callback(new RPCError('getblockheader "hash" ( verbose )'));
 
   hash = utils.revHex(String(args[0]));
 
@@ -829,7 +829,7 @@ RPC.prototype.getblockheader = function getblockheader(args, callback) {
       return callback(err);
 
     if (!entry)
-      return callback(new Error('Block not found'));
+      return callback(new RPCError('Block not found'));
 
     if (!verbose)
       return callback(null, entry.toRaw().toString('hex', 0, 80));
@@ -908,7 +908,7 @@ RPC.prototype.blockToJSON = function blockToJSON(entry, block, txDetails, callba
 
 RPC.prototype.getchaintips = function getchaintips(args, callback) {
   if (args.help || args.length !== 0)
-    return callback(new Error('getchaintips'));
+    return callback(new RPCError('getchaintips'));
 
   callback(null, [{
     height: this.chain.height,
@@ -920,7 +920,7 @@ RPC.prototype.getchaintips = function getchaintips(args, callback) {
 
 RPC.prototype.getdifficulty = function getdifficulty(args, callback) {
   if (args.help || args.length !== 0)
-    return callback(new Error('getdifficulty'));
+    return callback(new RPCError('getdifficulty'));
 
   callback(null, this._getDifficulty());
 };
@@ -939,7 +939,7 @@ RPC.prototype.getrawmempool = function getrawmempool(args, callback) {
   var verbose;
 
   if (args.help || args.length > 1)
-    return callback(new Error('getrawmempool ( verbose )'));
+    return callback(new RPCError('getrawmempool ( verbose )'));
 
   verbose = false;
 
@@ -1003,7 +1003,7 @@ RPC.prototype.gettxout = function gettxout(args, callback) {
   var hash, index, mempool;
 
   if (args.help || args.length < 2 || args.length > 3)
-    return callback(new Error('gettxout "txid" n ( includemempool )'));
+    return callback(new RPCError('gettxout "txid" n ( includemempool )'));
 
   hash = utils.revHex(String(args[0]));
   index = Number(args[1]);
@@ -1046,7 +1046,7 @@ RPC.prototype.verifytxoutproof = function verifytxoutproof(args, callback) {
 
 RPC.prototype.gettxoutsetinfo = function gettxoutsetinfo(args, callback) {
   if (args.help || args.length !== 0)
-    return callback(new Error('gettxoutsetinfo'));
+    return callback(new RPCError('gettxoutsetinfo'));
 
   callback(null, {
     height: this.chain.height,
@@ -1061,7 +1061,7 @@ RPC.prototype.gettxoutsetinfo = function gettxoutsetinfo(args, callback) {
 
 RPC.prototype.verifychain = function verifychain(args, callback) {
   if (args.help || args.length > 2)
-    return callback(new Error('verifychain ( checklevel numblocks )'));
+    return callback(new RPCError('verifychain ( checklevel numblocks )'));
 
   callback();
 };
@@ -1077,7 +1077,7 @@ RPC.prototype.getblocktemplate = function getblocktemplate(args, callback) {
   var i, j, tx, deps, input, dep, block;
 
   if (args.help || args.length > 1)
-    return callback(new Error('getblocktemplate ( "jsonrequestobject" )'));
+    return callback(new RPCError('getblocktemplate ( "jsonrequestobject" )'));
 
   this.miner.createBlock(function(err, attempt) {
     if (err)
@@ -1136,14 +1136,14 @@ RPC.prototype.getmininginfo = function getmininginfo(args, callback) {
   var self = this;
 
   if (args.help || args.length !== 0)
-    return callback(new Error('getmininginfo'));
+    return callback(new RPCError('getmininginfo'));
 
   this.chain.db.getBlock(this.chain.tip.hash, function(err, block) {
     if (err)
       return callback(err);
 
     if (!block)
-      return callback(new Error('Block not found.'));
+      return callback(new RPCError('Block not found.'));
 
     self._hashps(120, -1, function(err, hashps) {
       if (err)
@@ -1170,7 +1170,7 @@ RPC.prototype.getnetworkhashps = function getnetworkhashps(args, callback) {
   var lookup, height;
 
   if (args.help || args.length > 2)
-    return callback(new Error('getnetworkhashps ( blocks height )'));
+    return callback(new RPCError('getnetworkhashps ( blocks height )'));
 
   lookup = args.length > 0 ? Number(args[0]) : 120;
   height = args.length > 1 ? Number(args[1]) : -1;
@@ -1179,14 +1179,14 @@ RPC.prototype.getnetworkhashps = function getnetworkhashps(args, callback) {
 };
 
 RPC.prototype.prioritisetransaction = function prioritisetransaction(args, callback) {
-  callback(new Error('Not implemented.'));
+  callback(new RPCError('Not implemented.'));
 };
 
 RPC.prototype.submitblock = function submitblock(args, callback) {
   var block;
 
   if (args.help || args.length < 1 || args.length > 2)
-    return callback(new Error('submitblock "hexdata" ( "jsonparametersobject" )'));
+    return callback(new RPCError('submitblock "hexdata" ( "jsonparametersobject" )'));
 
   block = bcoin.block.fromRaw(args[0], 'hex');
 
@@ -1230,7 +1230,7 @@ RPC.prototype._hashps = function _hashps(lookup, height, callback) {
           return callback(err);
 
         if (!entry)
-          return callback(new Error('Not found.'));
+          return callback(new RPCError('Not found.'));
 
         pb0 = entry;
         time = pb0.ts;
@@ -1280,7 +1280,7 @@ RPC.prototype.generate = function generate(args, callback) {
   var numblocks, hashes;
 
   if (args.help || args.length < 1 || args.length > 2)
-    return callback(new Error('generate numblocks ( maxtries )'));
+    return callback(new RPCError('generate numblocks ( maxtries )'));
 
   numblocks = Number(args[0]);
   hashes = [];
@@ -1304,7 +1304,7 @@ RPC.prototype.generatetoaddress = function generatetoaddress(args, callback) {
   var address;
 
   if (args.help || args.length < 2 || args.length > 3)
-    return callback(new Error('generatetoaddress numblocks address (maxtries)'));
+    return callback(new RPCError('generatetoaddress numblocks address (maxtries)'));
 
   address = this.miner.address;
   this.miner.address = bcoin.address.fromBase58(args[1]);
@@ -1327,27 +1327,27 @@ RPC.prototype.createrawtransaction = function createrawtransaction(args, callbac
   var keys, addrs, key, value, address, b58;
 
   if (args.help || args.length < 2 || args.length > 3) {
-    return callback(new Error('createrawtransaction'
+    return callback(new RPCError('createrawtransaction'
       + ' [{"txid":"id","vout":n},...]'
       + ' {"address":amount,"data":"hex",...}'
       + ' ( locktime )'));
   }
 
   if (!args[0] || !args[1])
-    return callback(new Error('Invalid parameter'));
+    return callback(new RPCError('Invalid parameter'));
 
   inputs = args[0];
   sendTo = args[1];
 
   if (!Array.isArray(inputs) || typeof sendTo !== 'object')
-    return callback(new Error('Invalid parameter'));
+    return callback(new RPCError('Invalid parameter'));
 
   tx = bcoin.tx();
 
   if (args.length > 2 && args[2] != null) {
     locktime = Number(args[2]);
     if (locktime < 0 || locktime > 0xffffffff)
-      return callback(new Error('Invalid parameter, locktime out of range'));
+      return callback(new RPCError('Invalid parameter, locktime out of range'));
     tx.locktime = locktime;
   }
 
@@ -1355,7 +1355,7 @@ RPC.prototype.createrawtransaction = function createrawtransaction(args, callbac
     input = inputs[i];
 
     if (!input)
-      return callback(new Error('Invalid parameter'));
+      return callback(new RPCError('Invalid parameter'));
 
     hash = input.txid;
     index = input.vout;
@@ -1368,12 +1368,12 @@ RPC.prototype.createrawtransaction = function createrawtransaction(args, callbac
         || hash.length !== 64
         || !utils.isNumber(index)
         || index < 0) {
-      return callback(new Error('Invalid parameter'));
+      return callback(new RPCError('Invalid parameter'));
     }
 
     if (utils.isNumber(input.sequence)) {
       if (input.sequence < 0 || input.sequence > 0xffffffff)
-        return callback(new Error('Invalid parameter'));
+        return callback(new RPCError('Invalid parameter'));
       sequence = input.sequence;
     }
 
@@ -1409,7 +1409,7 @@ RPC.prototype.createrawtransaction = function createrawtransaction(args, callbac
     b58 = address.toBase58();
 
     if (addrs[b58])
-      return callback(new Error('Duplicate address'));
+      return callback(new RPCError('Duplicate address'));
 
     addrs[b58] = true;
 
@@ -1428,10 +1428,10 @@ RPC.prototype.decoderawtransaction = function decoderawtransaction(args, callbac
   var tx;
 
   if (args.help || args.length !== 1)
-    return callback(new Error('decoderawtransaction "hexstring"'));
+    return callback(new RPCError('decoderawtransaction "hexstring"'));
 
   if (!utils.isHex(args[0]))
-    return callback(new Error('Invalid parameter'));
+    return callback(new RPCError('Invalid parameter'));
 
   tx = bcoin.tx.fromRaw(args[0], 'hex');
 
@@ -1442,7 +1442,7 @@ RPC.prototype.decodescript = function decodescript(args, callback) {
   var data, script, hash, address;
 
   if (args.help || args.length !== 1)
-    return callback(new Error('decodescript \"hex\"'));
+    return callback(new RPCError('decodescript \"hex\"'));
 
   data = String(args[0]);
   script = new bcoin.script();
@@ -1464,12 +1464,12 @@ RPC.prototype.getrawtransaction = function getrawtransaction(args, callback) {
   var hash, verbose;
 
   if (args.help || args.length < 1 || args.length > 2)
-    return callback(new Error('getrawtransaction "txid" ( verbose )'));
+    return callback(new RPCError('getrawtransaction "txid" ( verbose )'));
 
   hash = args[0];
 
   if (!utils.isHex(hash) || hash.length !== 64)
-    return callback(new Error('Invalid parameter'));
+    return callback(new RPCError('Invalid parameter'));
 
   verbose = false;
 
@@ -1481,7 +1481,7 @@ RPC.prototype.getrawtransaction = function getrawtransaction(args, callback) {
       return callback(err);
 
     if (!tx)
-      return callback(new Error('No information available about transaction'));
+      return callback(new RPCError('No information available about transaction'));
 
     if (!verbose)
       return callback(null, tx.toRaw().toString('hex'));
@@ -1497,12 +1497,12 @@ RPC.prototype.sendrawtransaction = function sendrawtransaction(args, callback) {
   var tx;
 
   if (args.help || args.length < 1 || args.length > 2) {
-    return callback(new Error('sendrawtransaction'
+    return callback(new RPCError('sendrawtransaction'
       + ' "hexstring" ( allowhighfees )'));
     }
 
   if (!utils.isHex(args[0]))
-    return callback(new Error('Invalid parameter'));
+    return callback(new RPCError('Invalid parameter'));
 
   tx = bcoin.tx.fromRaw(args[0], 'hex');
 
@@ -1516,7 +1516,7 @@ RPC.prototype.signrawtransaction = function signrawtransaction(args, callback) {
   var raw, p, txs, merged;
 
   if (args.help || args.length < 1 || args.length > 4) {
-    return callback(new Error('signrawtransaction'
+    return callback(new RPCError('signrawtransaction'
       + ' "hexstring" ('
       + ' [{"txid":"id","vout":n,"scriptPubKey":"hex",'
       + 'redeemScript":"hex"},...] ["privatekey1",...]'
@@ -1557,7 +1557,7 @@ RPC.prototype._signrawtransaction = function signrawtransaction(merged, txs, arg
     for (i = 0; i < k.length; i++) {
       secret = k[i];
       if (!utils.isBase58(secret))
-        return callback(new Error('Invalid parameter'));
+        return callback(new RPCError('Invalid parameter'));
       key = bcoin.keypair.fromSecret(secret);
       addr = new bcoin.keyring({ publicKey: key.getPublicKey() });
       key = { addr: addr, key: key.getPrivateKey() };
@@ -1572,7 +1572,7 @@ RPC.prototype._signrawtransaction = function signrawtransaction(merged, txs, arg
     for (i = 0; i < prevout.length; i++) {
       prev = prevout[i];
       if (!prev)
-        return callback(new Error('Invalid parameter'));
+        return callback(new RPCError('Invalid parameter'));
       hash = prev.txid;
       index = prev.vout;
       script = prev.scriptPubKey;
@@ -1582,7 +1582,7 @@ RPC.prototype._signrawtransaction = function signrawtransaction(merged, txs, arg
           || !utils.isNumber(index)
           || index < 0
           || !utils.isHex(script)) {
-        return callback(new Error('Invalid parameter'));
+        return callback(new RPCError('Invalid parameter'));
       }
 
       script = bcoin.script.fromRaw(script, 'hex');
@@ -1624,12 +1624,12 @@ RPC.prototype._signrawtransaction = function signrawtransaction(merged, txs, arg
     parts = args[3].split('|');
     type = constants.hashType[parts[0]];
     if (type == null)
-      return callback(new Error('Invalid parameter'));
+      return callback(new RPCError('Invalid parameter'));
     if (parts.length > 2)
-      return callback(new Error('Invalid parameter'));
+      return callback(new RPCError('Invalid parameter'));
     if (parts.length === 2) {
       if (parts[1] !== 'ANYONECANPAY')
-        return callback(new Error('Invalid parameter'));
+        return callback(new RPCError('Invalid parameter'));
       type |= constants.hashType.ANYONECANPAY;
     }
   }
@@ -1690,7 +1690,7 @@ RPC.prototype._createRedeem = function _createRedeem(args, callback) {
       || args[0] < 1
       || args[1].length < args[0]
       || args[1].length > 16) {
-    return callback(new Error('Invalid parameter.'));
+    return callback(new RPCError('Invalid parameter.'));
   }
 
   m = args[0];
@@ -1700,21 +1700,21 @@ RPC.prototype._createRedeem = function _createRedeem(args, callback) {
   utils.forEachSerial(keys, function(key, next, i) {
     if (!utils.isBase58(key)) {
       if (!utils.isHex(key))
-        return next(new Error('Invalid key.'));
+        return next(new RPCError('Invalid key.'));
       keys[i] = new Buffer(key, 'hex');
       return next();
     }
 
     hash = bcoin.address.getHash(key, 'hex');
     if (!hash)
-      return next(new Error('Invalid key.'));
+      return next(new RPCError('Invalid key.'));
 
     self.node.wallet.getKeyring(hash, function(err, address) {
       if (err)
         return next(err);
 
       if (!address)
-        return next(new Error('Invalid key.'));
+        return next(new RPCError('Invalid key.'));
 
       keys[i] = address.getPublicKey();
 
@@ -1727,7 +1727,7 @@ RPC.prototype._createRedeem = function _createRedeem(args, callback) {
     script = bcoin.script.fromMultisig(m, n, keys);
 
     if (script.toRaw().length > constants.script.MAX_PUSH)
-      return callback(new Error('Redeem script exceeds size limit.'));
+      return callback(new RPCError('Redeem script exceeds size limit.'));
 
     callback(null, script);
   });
@@ -1736,7 +1736,7 @@ RPC.prototype._createRedeem = function _createRedeem(args, callback) {
 /* Utility functions */
 RPC.prototype.createmultisig = function createmultisig(args, callback) {
   if (args.help || args.length < 2 || args.length > 2)
-    return callback(new Error('createmultisig nrequired ["key",...]'));
+    return callback(new RPCError('createmultisig nrequired ["key",...]'));
 
   this._createRedeem(args, function(err, script) {
     if (err)
@@ -1770,12 +1770,12 @@ RPC.prototype.createwitnessaddress = function createwitnessaddress(args, callbac
   var raw, script, program;
 
   if (args.help || args.length !== 1)
-    return callback(new Error('createwitnessaddress "script"'));
+    return callback(new RPCError('createwitnessaddress "script"'));
 
   raw = args[1];
 
   if (!utils.isHex(raw))
-    return callback(new Error('Invalid parameter'));
+    return callback(new RPCError('Invalid parameter'));
 
   script = bcoin.script.fromRaw(raw, 'hex');
   program = this._scriptForWitness(script);
@@ -1790,7 +1790,7 @@ RPC.prototype.validateaddress = function validateaddress(args, callback) {
   var b58, address, json;
 
   if (args.help || args.length !== 1)
-    return callback(new Error('validateaddress "bitcoinaddress"'));
+    return callback(new RPCError('validateaddress "bitcoinaddress"'));
 
   b58 = String(args[0]);
 
@@ -1830,7 +1830,7 @@ RPC.prototype.verifymessage = function verifymessage(args, callback) {
   var address, sig, msg, key;
 
   if (args.help || args.length !== 3) {
-    return callback(new Error('verifymessage'
+    return callback(new RPCError('verifymessage'
       + ' "bitcoinaddress" "signature" "message"'));
   }
 
@@ -1841,7 +1841,7 @@ RPC.prototype.verifymessage = function verifymessage(args, callback) {
   address = bcoin.address.getHash(address);
 
   if (!address)
-    return callback(new Error('Invalid address.'));
+    return callback(new RPCError('Invalid address.'));
 
   sig = new Buffer(sig, 'base64');
   msg = new Buffer(RPC.magic + msg, 'utf8');
@@ -1861,7 +1861,7 @@ RPC.prototype.signmessagewithprivkey = function signmessagewithprivkey(args, cal
   var key, msg, sig;
 
   if (args.help || args.length !== 2)
-    return callback(new Error('signmessagewithprivkey "privkey" "message"'));
+    return callback(new RPCError('signmessagewithprivkey "privkey" "message"'));
 
   key = String(args[0]);
   msg = String(args[1]);
@@ -1879,7 +1879,7 @@ RPC.prototype.estimatefee = function estimatefee(args, callback) {
   var blocks, fee;
 
   if (args.help || args.length !== 1)
-    return callback(new Error('estimatefee nblocks'));
+    return callback(new RPCError('estimatefee nblocks'));
 
   blocks = Number(args[0]);
 
@@ -1903,7 +1903,7 @@ RPC.prototype.estimatepriority = function estimatepriority(args, callback) {
   var blocks, pri;
 
   if (args.help || args.length !== 1)
-    return callback(new Error('estimatepriority nblocks'));
+    return callback(new RPCError('estimatepriority nblocks'));
 
   blocks = Number(args[0]);
 
@@ -1922,7 +1922,7 @@ RPC.prototype.estimatesmartfee = function estimatesmartfee(args, callback) {
   var blocks, fee;
 
   if (args.help || args.length !== 1)
-    return callback(new Error('estimatesmartfee nblocks'));
+    return callback(new RPCError('estimatesmartfee nblocks'));
 
   blocks = Number(args[0]);
 
@@ -1949,7 +1949,7 @@ RPC.prototype.estimatesmartpriority = function estimatesmartpriority(args, callb
   var blocks, pri;
 
   if (args.help || args.length !== 1)
-    return callback(new Error('estimatesmartpriority nblocks'));
+    return callback(new RPCError('estimatesmartpriority nblocks'));
 
   blocks = Number(args[0]);
 
@@ -1971,12 +1971,12 @@ RPC.prototype.invalidateblock = function invalidateblock(args, callback) {
   var hash;
 
   if (args.help || args.length !== 1)
-    return callback(new Error('invalidateblock "hash"'));
+    return callback(new RPCError('invalidateblock "hash"'));
 
   hash = args[0];
 
   if (!utils.isHex(hash) || hash.length !== 64)
-    return callback(new Error('Block not found.'));
+    return callback(new RPCError('Block not found.'));
 
   hash = utils.revHex(hash);
 
@@ -1989,12 +1989,12 @@ RPC.prototype.reconsiderblock = function reconsiderblock(args, callback) {
   var hash;
 
   if (args.help || args.length !== 1)
-    return callback(new Error('reconsiderblock "hash"'));
+    return callback(new RPCError('reconsiderblock "hash"'));
 
   hash = args[0];
 
   if (!utils.isHex(hash) || hash.length !== 64)
-    return callback(new Error('Block not found.'));
+    return callback(new RPCError('Block not found.'));
 
   hash = utils.revHex(hash);
 
@@ -2007,12 +2007,12 @@ RPC.prototype.setmocktime = function setmocktime(args, callback) {
   var time, delta;
 
   if (args.help || args.length !== 1)
-    return callback(new Error('setmocktime timestamp'));
+    return callback(new RPCError('setmocktime timestamp'));
 
   time = args[0];
 
   if (!utils.isNumber(time))
-    return callback(new Error('Invalid parameter.'));
+    return callback(new RPCError('Invalid parameter.'));
 
   delta = bcoin.now() - time;
   bcoin.time.offset = -delta;
@@ -2030,7 +2030,7 @@ RPC.prototype.resendwallettransactions = function resendwallettransactions(args,
   var i, tx;
 
   if (args.help || args.length !== 0)
-    return callback(new Error('resendwallettransactions'));
+    return callback(new RPCError('resendwallettransactions'));
 
   this.walletdb.getUnconfirmed(function(err, txs) {
     if (err)
@@ -2048,7 +2048,7 @@ RPC.prototype.resendwallettransactions = function resendwallettransactions(args,
 
 RPC.prototype.addmultisigaddress = function addmultisigaddress(args, callback) {
   if (args.help || args.length < 2 || args.length > 3) {
-    return callback(new Error('addmultisigaddress'
+    return callback(new RPCError('addmultisigaddress'
       + ' nrequired ["key",...] ( "account" )'));
   }
   // Impossible to implement in bcoin (no address book).
@@ -2057,14 +2057,14 @@ RPC.prototype.addmultisigaddress = function addmultisigaddress(args, callback) {
 
 RPC.prototype.addwitnessaddress = function addwitnessaddress(args, callback) {
   if (args.help || args.length < 1 || args.length > 1)
-    return callback(new Error('addwitnessaddress \"address\"'));
+    return callback(new RPCError('addwitnessaddress \"address\"'));
   // Unlikely to be implemented.
   callback(new Error('Not implemented.'));
 };
 
 RPC.prototype.backupwallet = function backupwallet(args, callback) {
   if (args.help || args.length !== 1)
-    return callback(new Error('backupwallet "destination"'));
+    return callback(new RPCError('backupwallet "destination"'));
   // Unlikely to be implemented.
   callback(new Error('Not implemented.'));
 };
@@ -2074,24 +2074,24 @@ RPC.prototype.dumpprivkey = function dumpprivkey(args, callback) {
   var hash, key;
 
   if (args.help || args.length !== 1)
-    return callback(new Error('dumpprivkey "bitcoinaddress"'));
+    return callback(new RPCError('dumpprivkey "bitcoinaddress"'));
 
   hash = bcoin.address.getHash(String(args[0]), 'hex');
 
   if (!hash)
-    return callback(new Error('Invalid address.'));
+    return callback(new RPCError('Invalid address.'));
 
   this.wallet.getKeyring(hash, function(err, ring) {
     if (err)
       return callback(err);
 
     if (!ring)
-      return callback(new Error('Key not found.'));
+      return callback(new RPCError('Key not found.'));
 
     key = self.wallet.master.key;
 
     if (!key)
-      return callback(new Error('Wallet is locked.'));
+      return callback(new RPCError('Wallet is locked.'));
 
     key = key.deriveAccount44(ring.account);
     key = key.derive(ring.change).derive(ring.index);
@@ -2105,7 +2105,7 @@ RPC.prototype.dumpwallet = function dumpwallet(args, callback) {
   var file, time, key, address, fmt, str, out;
 
   if (args.help || args.length !== 1)
-    return callback(new Error('dumpwallet "filename"'));
+    return callback(new RPCError('dumpwallet "filename"'));
 
   file = utils.normalize(String(args[0]));
   time = utils.date();
@@ -2134,7 +2134,7 @@ RPC.prototype.dumpwallet = function dumpwallet(args, callback) {
         key = self.wallet.master.key;
 
         if (!key)
-          return callback(new Error('Wallet is locked.'));
+          return callback(new RPCError('Wallet is locked.'));
 
         key = key.deriveAccount44(ring.account);
         key = key.derive(ring.change).derive(ring.index);
@@ -2169,15 +2169,15 @@ RPC.prototype.encryptwallet = function encryptwallet(args, callback) {
   var passphrase;
 
   if (!this.wallet.master.encrypted && (args.help || args.help !== 1))
-    return callback(new Error('encryptwallet "passphrase"'));
+    return callback(new RPCError('encryptwallet "passphrase"'));
 
   if (this.wallet.master.encrypted)
-    return callback(new Error('Already running with an encrypted wallet'));
+    return callback(new RPCError('Already running with an encrypted wallet'));
 
   passphrase = args[0];
 
   if (typeof passphrase !== 'string' || passphrase.length < 1)
-    return callback(new Error('encryptwallet "passphrase"'));
+    return callback(new RPCError('encryptwallet "passphrase"'));
 
   this.wallet.setPassphrase(passphrase, function(err) {
     if (err)
@@ -2190,7 +2190,7 @@ RPC.prototype.getaccountaddress = function getaccountaddress(args, callback) {
   var account;
 
   if (args.help || args.length !== 1)
-    return callback(new Error('getaccountaddress "account"'));
+    return callback(new RPCError('getaccountaddress "account"'));
 
   account = String(args[0]);
 
@@ -2212,12 +2212,12 @@ RPC.prototype.getaccount = function getaccount(args, callback) {
   var hash;
 
   if (args.help || args.length !== 1)
-    return callback(new Error('getaccount "bitcoinaddress"'));
+    return callback(new RPCError('getaccount "bitcoinaddress"'));
 
   hash = bcoin.address.getHash(args[0], 'hex');
 
   if (!hash)
-    return callback(new Error('Invalid address.'));
+    return callback(new RPCError('Invalid address.'));
 
   this.wallet.getKeyring(hash, function(err, address) {
     if (err)
@@ -2235,7 +2235,7 @@ RPC.prototype.getaddressesbyaccount = function getaddressesbyaccount(args, callb
   var account, addrs;
 
   if (args.help || args.length !== 1)
-    return callback(new Error('getaddressesbyaccount "account"'));
+    return callback(new RPCError('getaddressesbyaccount "account"'));
 
   account = String(args[0]);
 
@@ -2272,7 +2272,7 @@ RPC.prototype.getbalance = function getbalance(args, callback) {
   var account, value;
 
   if (args.help || args.length > 3)
-    return callback(new Error('getbalance ( "account" minconf includeWatchonly )'));
+    return callback(new RPCError('getbalance ( "account" minconf includeWatchonly )'));
 
   if (args.length >= 1) {
     account = String(args[0]);
@@ -2302,7 +2302,7 @@ RPC.prototype.getnewaddress = function getnewaddress(args, callback) {
   var account;
 
   if (args.help || args.length > 1)
-    return callback(new Error('getnewaddress ( "account" )'));
+    return callback(new RPCError('getnewaddress ( "account" )'));
 
   if (args.length === 1)
     account = String(args[0]);
@@ -2319,7 +2319,7 @@ RPC.prototype.getnewaddress = function getnewaddress(args, callback) {
 
 RPC.prototype.getrawchangeaddress = function getrawchangeaddress(args, callback) {
   if (args.help || args.length > 1)
-    return callback(new Error('getrawchangeaddress'));
+    return callback(new RPCError('getrawchangeaddress'));
 
   this.wallet.createChange(function(err, address) {
     if (err)
@@ -2335,7 +2335,7 @@ RPC.prototype.getreceivedbyaccount = function getreceivedbyaccount(args, callbac
   var i, j, account, tx, output;
 
   if (args.help || args.length < 1 || args.length > 2)
-    return callback(new Error('getreceivedbyaccount "account" ( minconf )'));
+    return callback(new RPCError('getreceivedbyaccount "account" ( minconf )'));
 
   account = String(args[0]);
 
@@ -2374,12 +2374,12 @@ RPC.prototype.getreceivedbyaddress = function getreceivedbyaddress(args, callbac
   var i, j, hash, tx, output;
 
   if (args.help || args.length < 1 || args.length > 2)
-    return callback(new Error('getreceivedbyaddress "bitcoinaddress" ( minconf )'));
+    return callback(new RPCError('getreceivedbyaddress "bitcoinaddress" ( minconf )'));
 
   hash = bcoin.address.getHash(String(args[0]), 'hex');
 
   if (!hash)
-    return callback(new Error('Invalid address'));
+    return callback(new RPCError('Invalid address'));
 
   if (args.length === 2)
     minconf = Number(args[1]);
@@ -2415,7 +2415,7 @@ RPC.prototype._toWalletTX = function _toWalletTX(tx, callback) {
       return callback(err);
 
     if (!map)
-      return callback(new Error('TX not found.'));
+      return callback(new RPCError('TX not found.'));
 
     receive = map.inputs.length === 0;
     member = receive ? map.outputs[0] : map.inputs[0];
@@ -2452,12 +2452,12 @@ RPC.prototype.gettransaction = function gettransaction(args, callback) {
   var hash;
 
   if (args.help || args.length < 1 || args.length > 2)
-    return callback(new Error('gettransaction "txid" ( includeWatchonly )'));
+    return callback(new RPCError('gettransaction "txid" ( includeWatchonly )'));
 
   hash = String(args[0]);
 
   if (!utils.isHex(hash) || hash.length !== 64)
-    return callback(new Error('Invalid parameter'));
+    return callback(new RPCError('Invalid parameter'));
 
   hash = utils.revHex(hash);
 
@@ -2466,7 +2466,7 @@ RPC.prototype.gettransaction = function gettransaction(args, callback) {
       return callback(err);
 
     if (!tx)
-      return callback(new Error('TX not found.'));
+      return callback(new RPCError('TX not found.'));
 
     self._toWalletTX(tx, callback);
   });
@@ -2478,7 +2478,7 @@ RPC.prototype.abandontransaction = function abandontransaction(args, callback) {
 
 RPC.prototype.getunconfirmedbalance = function getunconfirmedbalance(args, callback) {
   if (args.help || args.length > 0)
-    return callback(new Error('getunconfirmedbalance'));
+    return callback(new RPCError('getunconfirmedbalance'));
 
   this.wallet.getBalance(function(err, balance) {
     if (err)
@@ -2492,7 +2492,7 @@ RPC.prototype.getwalletinfo = function getwalletinfo(args, callback) {
   var self = this;
 
   if (args.help || args.length !== 0)
-    return callback(new Error('getwalletinfo'));
+    return callback(new RPCError('getwalletinfo'));
 
   this.wallet.getBalance(function(err, balance) {
     if (err)
@@ -2520,7 +2520,7 @@ RPC.prototype.getwalletinfo = function getwalletinfo(args, callback) {
 
 RPC.prototype.importprivkey = function importprivkey(args, callback) {
   if (args.help || args.length < 1 || args.length > 3) {
-    return callback(new Error('importprivkey'
+    return callback(new RPCError('importprivkey'
       + ' "bitcoinprivkey" ( "label" rescan )'));
   }
   // Impossible to implement in bcoin.
@@ -2529,14 +2529,14 @@ RPC.prototype.importprivkey = function importprivkey(args, callback) {
 
 RPC.prototype.importwallet = function importwallet(args, callback) {
   if (args.help || args.length !== 1)
-    return callback(new Error('importwallet "filename"'));
+    return callback(new RPCError('importwallet "filename"'));
   // Impossible to implement in bcoin.
   callback(new Error('Not implemented.'));
 };
 
 RPC.prototype.importaddress = function importaddress(args, callback) {
   if (args.help || args.length < 1 || args.length > 4) {
-    return callback(new Error('importaddress'
+    return callback(new RPCError('importaddress'
       + ' "address" ( "label" rescan p2sh )'));
   }
   // Impossible to implement in bcoin.
@@ -2545,14 +2545,14 @@ RPC.prototype.importaddress = function importaddress(args, callback) {
 
 RPC.prototype.importpubkey = function importpubkey(args, callback) {
   if (args.help || args.length < 1 || args.length > 4)
-    return callback(new Error('importpubkey "pubkey" ( "label" rescan )'));
+    return callback(new RPCError('importpubkey "pubkey" ( "label" rescan )'));
   // Impossible to implement in bcoin.
   callback(new Error('Not implemented.'));
 };
 
 RPC.prototype.keypoolrefill = function keypoolrefill(args, callback) {
   if (args.help || args.length > 1)
-    return callback(new Error('keypoolrefill ( newsize )'));
+    return callback(new RPCError('keypoolrefill ( newsize )'));
   callback(null, null);
 };
 
@@ -2561,7 +2561,7 @@ RPC.prototype.listaccounts = function listaccounts(args, callback) {
   var map;
 
   if (args.help || args.length > 2)
-    return callback(new Error('listaccounts ( minconf includeWatchonly)'));
+    return callback(new RPCError('listaccounts ( minconf includeWatchonly)'));
 
   map = {};
 
@@ -2588,7 +2588,7 @@ RPC.prototype.listaccounts = function listaccounts(args, callback) {
 
 RPC.prototype.listaddressgroupings = function listaddressgroupings(args, callback) {
   if (args.help)
-    return callback(new Error('listaddressgroupings'));
+    return callback(new RPCError('listaddressgroupings'));
   callback(new Error('Not implemented.'));
 };
 
@@ -2609,14 +2609,14 @@ RPC.prototype.listsinceblock = function listsinceblock(args, callback) {
   var block, conf, out, highest;
 
   if (args.help) {
-    return callback(new Error('listsinceblock'
+    return callback(new RPCError('listsinceblock'
       + ' ( "blockhash" target-confirmations includeWatchonly)'));
   }
 
   if (args.length > 0) {
     block = String(args[0]);
     if (!utils.isHex(block) || block.length !== 64)
-      return callback(new Error('Invalid parameter.'));
+      return callback(new RPCError('Invalid parameter.'));
     block = utils.revHex(block);
   }
 
@@ -2625,7 +2625,7 @@ RPC.prototype.listsinceblock = function listsinceblock(args, callback) {
   if (args.length > 1) {
     conf = Number(args[1]);
     if (!utils.isNumber(conf) || conf < 0)
-      return callback(new Error('Invalid parameter.'));
+      return callback(new RPCError('Invalid parameter.'));
   }
 
   out = [];
@@ -2680,7 +2680,7 @@ RPC.prototype._toListTX = function _toListTX(tx, callback) {
       return callback(err);
 
     if (!map)
-      return callback(new Error('TX not found.'));
+      return callback(new RPCError('TX not found.'));
 
     receive = map.inputs.length === 0;
     member = receive ? map.outputs[0] : map.inputs[0];
@@ -2713,7 +2713,7 @@ RPC.prototype.listtransactions = function listtransactions(args, callback) {
   var account, count;
 
   if (args.help || args.length > 4) {
-    return callback(new Error('listtransactions'
+    return callback(new RPCError('listtransactions'
       + ' ( "account" count from includeWatchonly)'));
   }
 
@@ -2782,7 +2782,7 @@ RPC.prototype.sendfrom = function sendfrom(args, callback) {
   var account, address, amount;
 
   if (args.help || args.length < 3 || args.length > 6) {
-    return callback(new Error('sendfrom'
+    return callback(new RPCError('sendfrom'
       + ' "fromaccount" "tobitcoinaddress"'
       + ' amount ( minconf "comment" "comment-to" )'));
   }
@@ -2809,7 +2809,7 @@ RPC.prototype.sendtoaddress = function sendtoaddress(args, callback) {
   var address, amount, subtractFee;
 
   if (args.help || args.length < 2 || args.length > 5) {
-    return callback(new Error('sendtoaddress'
+    return callback(new RPCError('sendtoaddress'
       + ' "bitcoinaddress" amount'
       + ' ( "comment" "comment-to"'
       + ' subtractfeefromamount )'));
@@ -2828,14 +2828,14 @@ RPC.prototype.sendtoaddress = function sendtoaddress(args, callback) {
 
 RPC.prototype.setaccount = function setaccount(args, callback) {
   if (args.help || args.length < 1 || args.length > 2)
-    return callback(new Error('setaccount "bitcoinaddress" "account"'));
+    return callback(new RPCError('setaccount "bitcoinaddress" "account"'));
   // Impossible to implement in bcoin:
   callback(new Error('Not implemented.'));
 };
 
 RPC.prototype.settxfee = function settxfee(args, callback) {
   if (args.help || args.length < 1 || args.length > 1)
-    return callback(new Error('settxfee amount'));
+    return callback(new RPCError('settxfee amount'));
 
   this.feeRate = utils.satoshi(args[0]);
 
@@ -2847,7 +2847,7 @@ RPC.prototype.signmessage = function signmessage(args, callback) {
   var address, msg, key, sig;
 
   if (args.help || args.length !== 2)
-    return callback(new Error('signmessage "bitcoinaddress" "message"'));
+    return callback(new RPCError('signmessage "bitcoinaddress" "message"'));
 
   address = String(args[0]);
   msg = String(args[1]);
@@ -2855,19 +2855,19 @@ RPC.prototype.signmessage = function signmessage(args, callback) {
   address = bcoin.address.getHash(address, 'hex');
 
   if (!address)
-    return callback(new Error('Invalid address.'));
+    return callback(new RPCError('Invalid address.'));
 
   this.wallet.getKeyring(address, function(err, address) {
     if (err)
       return callback(err);
 
     if (!address)
-      return callback(new Error('Address not found.'));
+      return callback(new RPCError('Address not found.'));
 
     key = self.wallet.master.key;
 
     if (!key)
-      return callback(new Error('Wallet is locked.'));
+      return callback(new RPCError('Wallet is locked.'));
 
     key = key.deriveAccount44(address.account);
     key = key.derive(address.change).derive(address.index);
@@ -2883,10 +2883,10 @@ RPC.prototype.signmessage = function signmessage(args, callback) {
 
 RPC.prototype.walletlock = function walletlock(args, callback) {
   if (args.help || (this.wallet.master.encrypted && args.length !== 0))
-    return callback(new Error('walletlock'));
+    return callback(new RPCError('walletlock'));
 
   if (!this.wallet.master.encrypted)
-    return callback(new Error('Wallet is not encrypted.'));
+    return callback(new RPCError('Wallet is not encrypted.'));
 
   this.wallet.lock();
   callback(null, null);
@@ -2896,21 +2896,21 @@ RPC.prototype.walletpassphrasechange = function walletpassphrasechange(args, cal
   var old, new_;
 
   if (args.help || (this.wallet.master.encrypted && args.length !== 2)) {
-    return callback(new Error('walletpassphrasechange'
+    return callback(new RPCError('walletpassphrasechange'
       + ' "oldpassphrase" "newpassphrase"'));
   }
 
   if (!this.wallet.master.encrypted)
-    return callback(new Error('Wallet is not encrypted.'));
+    return callback(new RPCError('Wallet is not encrypted.'));
 
   if (typeof args[0] !== 'string' || typeof args[1] !== 'string')
-    return callback(new Error('Invalid parameter'));
+    return callback(new RPCError('Invalid parameter'));
 
   old = args[0];
   new_ = args[1];
 
   if (old.length < 1 || new_.length < 1)
-    return callback(new Error('Invalid parameter'));
+    return callback(new RPCError('Invalid parameter'));
 
   this.wallet.setPassphrase(old, new_, function(err) {
     if (err)
@@ -2922,16 +2922,16 @@ RPC.prototype.walletpassphrasechange = function walletpassphrasechange(args, cal
 
 RPC.prototype.walletpassphrase = function walletpassphrase(args, callback) {
   if (args.help || (this.wallet.master.encrypted && args.length !== 2))
-    return callback(new Error('walletpassphrase "passphrase" timeout'));
+    return callback(new RPCError('walletpassphrase "passphrase" timeout'));
 
   if (!this.wallet.master.encrypted)
-    return callback(new Error('Wallet is not encrypted.'));
+    return callback(new RPCError('Wallet is not encrypted.'));
 
   if (typeof args[0] !== 'string' || args[0].length < 1)
-    return callback(new Error('Invalid parameter'));
+    return callback(new RPCError('Invalid parameter'));
 
   if (!utils.isNumber(args[1]) || args[1] < 0)
-    return callback(new Error('Invalid parameter'));
+    return callback(new RPCError('Invalid parameter'));
 
   this.wallet.unlock(args[0], args[1], function(err) {
     if (err)
@@ -2940,4 +2940,20 @@ RPC.prototype.walletpassphrase = function walletpassphrase(args, callback) {
   });
 };
 
+/*
+ * Helpers
+ */
+
+function RPCError(msg) {
+  Error.call(this);
+
+  if (Error.captureStackTrace)
+    Error.captureStackTrace(this, RPCError);
+
+  this.type = 'RPCError';
+  this.message = msg;
+}
+
+utils.inherits(RPCError, Error);
+
 module.exports = RPC;
diff --git a/lib/bcoin/http/server.js b/lib/bcoin/http/server.js
index bafb4c8d..a785e6c4 100644
--- a/lib/bcoin/http/server.js
+++ b/lib/bcoin/http/server.js
@@ -333,7 +333,16 @@ HTTPServer.prototype._init = function _init() {
     self.rpc.execute(req.body, function(err, json) {
       if (err) {
         self.logger.error(err);
-        return send(400, {
+
+        if (err.type === 'RPCError') {
+          return send(400, {
+            result: err.message,
+            error: null,
+            id: req.body.id
+          });
+        }
+
+        return send(500, {
           result: null,
           error: {
             message: err.message,
@@ -342,6 +351,7 @@ HTTPServer.prototype._init = function _init() {
           id: req.body.id
         });
       }
+
       send(200, {
         result: json,
         error: null,