x402-tool-server

Fastify middleware for x402 HTTP-payment-gated tool endpoints. Gate any API behind Solana USDC micropayments — agents handle the 402 challenge-response flow automatically.

Install

pnpm add x402-tool-server x402-adapters

Quick Start

import Fastify from 'fastify';
import { x402PaymentMiddleware, defineTool } from 'x402-tool-server';
import { MockVerifier } from 'x402-adapters';

const app = Fastify();
const verifier = new MockVerifier();

app.register(x402PaymentMiddleware, { verifier });

app.get('/weather', {
  config: defineTool({
    name: 'weather',
    description: 'Get current weather',
    price: '0.001',
    recipient: 'your-wallet-address',
  }),
}, async () => {
  return { temp: 22, unit: 'C', conditions: 'sunny' };
});

app.listen({ port: 3000 });

Features

• Fastify-native middleware (the only x402 implementation for Fastify)
• Automatic 402 challenge generation with nonce, price, and recipient
• On-chain payment verification via pluggable adapters
• Request hash binding prevents proof replay across endpoints
• Nonce-based replay protection
• Idempotency store for receipt tracking

Links

• GitHub
• Playground
• x402 Protocol