CryptoAPIs MCP Signer

MCP server for local transaction signing across EVM, UTXO, Tron, and XRP blockchains — no API calls required

GitHub

@cryptoapis-io/mcp-signer

MCP server for local transaction signing across EVM, UTXO, Tron, and XRP blockchains. 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 / secret as 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).

ActionDescription
sign-from-detailsSign from structured transaction fields (to, value, gasLimit, etc.)
sign-unsigned-hexSign a pre-built unsigned transaction hex

utxo_sign

Sign a UTXO transaction (Bitcoin, Bitcoin Cash, Litecoin, Dogecoin, Dash, Zcash).

ActionDescription
sign-from-detailsSign from a prepared transaction object (inputs, outputs)
sign-unsigned-hexSign a raw unsigned transaction hex with input descriptors

tron_sign

Sign a Tron transaction using secp256k1 (no TronWeb dependency).

ActionDescription
sign-from-detailsSign from a transaction object with raw_data_hex
sign-unsigned-hexSign a pre-built unsigned transaction hex

xrp_sign

Sign an XRP transaction.

ActionDescription
sign-from-detailsSign from structured XRP transaction fields
sign-unsigned-hexSign a pre-built unsigned transaction hex

All tools return signedTransactionHex — ready to broadcast with @cryptoapis-io/mcp-broadcast.

Dependencies

PackagePurpose
ethersEVM transaction signing
bitcoinjs-lib + ecpair + tiny-secp256k1UTXO transaction signing
ellipticTron transaction signing (secp256k1)
xrplXRP transaction signing

License

MIT

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