x402: Agent Payments

npm i @x402/express @x402/core @x402/evm

import express from "express";
import { paymentMiddleware, x402ResourceServer } from "@x402/express";
import { HTTPFacilitatorClient, type RoutesConfig } from "@x402/core/server";
import { ExactEvmScheme } from "@x402/evm/exact/server";

// Celo's hosted facilitator — note the api. subdomain
const facilitator = new HTTPFacilitatorClient({
  url: "https://api.x402.celo.org",
  // Attaches your metering key to every facilitator request. /settle is
  // key-gated; without a valid key it returns 401 Missing X-API-Key.
  createAuthHeaders: async () => {
    const h = { "X-API-Key": process.env.X402_API_KEY! };
    return { verify: h, settle: h, supported: h };
  },
});

const server = new x402ResourceServer(facilitator);
server.register("eip155:*", new ExactEvmScheme());

// The RoutesConfig annotation is load-bearing: without it `network` widens to
// `string` and no longer satisfies the CAIP-2 `${string}:${string}` type.
const routes: RoutesConfig = {
  "GET /premium": {
    accepts: [
      {
        scheme: "exact",
        network: "eip155:42220", // Celo mainnet
        payTo: "0xYourSellerPayoutAddress", // your wallet — receives the USDC
        price: {
          amount: "10000", // $0.01 — USDC has 6 decimals; always a string
          asset: "0xcEBA9300f2b948710d2653dD7B07f33A8B32118C",
          extra: { name: "USDC", version: "2" }, // EIP-712 domain, must match the token
        },
      },
    ],
    description: "Premium content",
  },
};

const app = express();
app.use(paymentMiddleware(routes, server)); // routes first, then server
app.get("/premium", (_req, res) => res.json({ data: "paid content" }));
app.listen(3000);

// Mainnet
const mainnetAccepts = {
  scheme: "exact",
  network: "eip155:42220",
  payTo: "0xYourSellerPayoutAddress",
  price: {
    amount: "10000", // $0.01 — USDC has 6 decimals
    asset: "0xcEBA9300f2b948710d2653dD7B07f33A8B32118C", // Celo mainnet USDC
    extra: { name: "USDC", version: "2" },
  },
};

// Testnet (Celo Sepolia)
const testnetAccepts = {
  scheme: "exact",
  network: "eip155:11142220",
  payTo: "0xYourSellerPayoutAddress",
  price: {
    amount: "10000", // $0.01 — USDC has 6 decimals
    asset: "0x01C5C0122039549AD1493B8220cABEdD739BC44E", // Celo Sepolia USDC
    extra: { name: "USDC", version: "2" },
  },
};