X402 MCP server

x402-mcp-server

A small, growing catalog of x402-paywalled HTTP tools on Base Mainnet via x402 micro-payments — no API keys, no signup, pay per call in USDC.

This MCP server exposes that catalog as native MCP tools. Every tool call pays for itself automatically: the server POSTs the request, catches the real x402 v2 402 PAYMENT-REQUIRED challenge, signs an EIP-3009 TransferWithAuthorization with viem using a local wallet, and resubmits with the PAYMENT-SIGNATURE header. No human signature prompt at call time — the agent just calls the tool.

Tools

<!-- BEGIN GENERATED TOOLS TABLE -- do not hand-edit, generated by generate-mcp.mjs -->

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All tools run on Base Mainnet (eip155:8453), settled through the x402.primer.systems facilitator. Exact request-body fields for each tool are also discoverable at runtime via /openapi.json.

Quickstart

Add this to your claudedesktopconfig.json:

{
  "mcpServers": {
    "x402-mcp-server": {
      "command": "npx",
      "args": ["-y", "x402-mcp-server_by_milza"],
      "env": {
        "BASE_PRIVATE_KEY": "0xyour_base_mainnet_private_key"
      }
    }
  }
}

⚠️ Funding warning: BASEPRIVATEKEY must be a Base Mainnet wallet private key funded with a small amount of real USDC (e.g. $0.50 is enough for dozens of calls at these prices). Every tool call spends real money from this wallet. Do not use a key that holds funds you're not prepared to spend through this server, and never commit this key to source control.

Once configured, restart Claude Desktop and the tools listed above become available to the assistant automatically — no further setup, no dashboard, no API key registration.

How payment works

Shortened. The full README is on GitHub.