Signer
Local transaction signing for EVM, UTXO, Tron, XRP, Kaspa, Solana and Tezos — no API calls
Runs on your machine from its package; the steps are below.
What it does
- Reads
- Writes
- High impact
At most: moves money, runs code or commands, deletes data, or sends messages for you.
What it costs
FreeOdel charges nothing per call. The publisher may charge for its own service.
Runs locally over stdio
This server isn't hosted — your MCP client launches it from a package registry. Use one of the commands below, or drop the config into your client (e.g. Claude Desktop).
Run
npx -y @cryptoapis-io/mcp-signer
MCP client config
{
"mcpServers": {
"signer": {
"command": "npx",
"args": [
"-y",
"@cryptoapis-io/mcp-signer"
]
}
}
}@cryptoapis-io/mcp-signer
MCP server for local transaction signing across EVM, UTXO, Tron, XRP, Kaspa, Solana and Tezos. No Crypto APIs HTTP calls — signing happens entirely on your machine. No API key required.
Security
- Stdio only — no HTTP transport. The server does not listen on any port.
- Private keys in tool input — each tool receives
privateKey/privateKeys/secretas parameters. Keys are never read from environment variables. - No network calls — all signing is done locally using cryptographic libraries.
Installation
npm install @cryptoapis-io/mcp-signer
Or install all Crypto APIs MCP servers: npm install @cryptoapis-io/mcp
Usage
npx @cryptoapis-io/mcp-signer
Claude Desktop
Add to your Claude Desktop config (~/Library/Application Support/Claude/claude_desktop_config.json on macOS, %APPDATA%\Claude\claude_desktop_config.json on Windows):
{
"mcpServers": {
"cryptoapis-signer": {
"command": "npx",
"args": ["-y", "@cryptoapis-io/mcp-signer"]
}
}
}
Cursor
Add to .cursor/mcp.json (project) or ~/.cursor/mcp.json (global):
{
"mcpServers": {
"cryptoapis-signer": {
"command": "npx",
"args": ["-y", "@cryptoapis-io/mcp-signer"]
}
}
}
MCP Inspector
npx @modelcontextprotocol/inspector npx @cryptoapis-io/mcp-signer
Available Tools
evm_sign
Sign an EVM transaction (Ethereum, Ethereum Classic, BSC, Polygon, Avalanche (C-Chain), Arbitrum, Base, Optimism, Tron).
| Action | Description |
|---|---|
sign-from-details | Sign from structured transaction fields (to, value, gasLimit, etc.) |
sign-unsigned-hex | Sign a pre-built unsigned transaction hex |
sign-typed-data | Sign an EIP-712 typed-data message (the x402 gasless path — e.g. the EIP-3009 TransferWithAuthorization from the x402 buyer /authorize). Returns { signature }, not a tx. |
utxo_sign
Sign a UTXO transaction (Bitcoin, Bitcoin Cash, Litecoin, Dogecoin, Dash, Zcash).
| Action | Description |
|---|---|
sign-from-details | Sign from a prepared transaction object (inputs, outputs) |
sign-unsigned-hex | Sign a raw unsigned transaction hex with input descriptors |
tron_sign
Sign a Tron transaction using secp256k1 (no TronWeb dependency).
| Action | Description |
|---|---|
sign-from-details | Sign from a transaction object with raw_data_hex |
sign-unsigned-hex | Sign a pre-built unsigned transaction hex |
xrp_sign
Sign an XRP transaction.
| Action | Description |
|---|---|
sign-from-details | Sign from structured XRP transaction fields |
sign-unsigned-hex | Sign a pre-built unsigned transaction hex |
kaspa_sign
Sign a Kaspa transaction using schnorr (BIP340) via kaspa-wasm. Mainnet only.
| Action | Description |
|---|---|
sign-from-details | Sign a prepared Kaspa transaction (from the prepare-transaction API) |
svm_sign
Partial-sign a Solana (SVM) x402 payment transaction — the buyer's source-authority signature only (the facilitator's feePayer slot stays unsigned, signed at settle).
| Action | Description |
|---|---|
partial-sign | Deserialize the base64 unsigned TransferChecked tx from the x402 buyer /authorize (scheme svm-transaction), add the buyer signature, re-serialize to base64. Returns { transaction }. |
tezos_sign
Sign a Tezos operation for tz1 (ed25519), tz2 (secp256k1) or tz3 (P-256) keys (edsk… / spsk… / p2sk…).
| Action | Description |
|---|---|
sign-forged-operation | Sign the forgedOperation hex from prepare_transactions_tezos. The operation is decoded first: only reveal/transaction ops from the key's own address are signed, and the optional expected (destination, amount in mutez, maxFee) must match. Returns { signedOperation, operationHash, signature, … }; broadcast signedOperation. |
Most tools return signedTransactionHex — ready to broadcast with @cryptoapis-io/mcp-broadcast. The
x402 paths return { signature } (EVM typed-data) or { transaction } (SVM) instead.
Dependencies
| Package | Purpose |
|---|---|
ethers | EVM transaction signing |
bitcoinjs-lib + ecpair + tiny-secp256k1 | UTXO transaction signing |
elliptic | Tron transaction signing (secp256k1) |
xrpl | XRP transaction signing |
License
MIT
