@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).

`utxo_sign`

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

`tron_sign`

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

`xrp_sign`

Sign an XRP transaction.

`kaspa_sign`

Sign a Kaspa transaction using schnorr (BIP340) via `kaspa-wasm`. Mainnet only.

`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).

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

License

MIT