x402-gateway-mcp

Stdio MCP server that exposes every x402-gateway data endpoint as an MCP tool and pays for calls with your wallet (USDC on Base, x402 protocol). Tool list is fetched from the gateway's /.well-known/x402.json at startup — new gateway endpoints appear automatically.

⚠️ Funded-wallet warning: WALLET_PRIVATE_KEY signs real payments. Use a dedicated wallet holding only small balances (a few dollars of USDC). Never your main wallet. The key is read from env, never logged, and payment headers are never echoed into agent-visible output.

5-minute setup (Claude Desktop / Claude Code)

1. Create a fresh wallet and fund it with a small amount of USDC on Base (or Base Sepolia test USDC from https://faucet.circle.com while testing).

2. npm install -g x402-gateway-mcp (or use npx).

3. Add to your MCP config (Claude Desktop claude_desktop_config.json, or claude mcp add for Claude Code):

{
  "mcpServers": {
    "x402-gateway": {
      "command": "npx",
      "args": ["-y", "x402-gateway-mcp"],
      "env": {
        "GATEWAY_URL": "https://<your-gateway-host>",
        "WALLET_PRIVATE_KEY": "0x<small-balance-wallet-key>",
        "MAX_PER_CALL_USD": "0.25",
        "MAX_SESSION_USD": "2.00"
      }
    }
  }
}

4. Restart the client. Every tool description states its price, e.g. [costs $0.005 USDC per call] Get the current USD price of a cryptocurrency…

Related MCP server: payclaw

Spend guardrails

• MAX_PER_CALL_USD (default 0.25): tools priced above this are refused. Note: the gateway's premium /report/domain dossier costs $1.00 — set MAX_PER_CALL_USD=1.25 to enable it; the default deliberately keeps premium tools opt-in.

• MAX_SESSION_USD (default 2.00): cumulative settled spend per server session; calls that would exceed it are refused with a clear message the agent can relay. Restart the server to reset.

Refusals happen before any payment is signed.

Env reference