@korateams/x402-sdk

Open-source Express middleware that makes any route on your own server machine-payable via the x402 protocol. Install it, wrap a route, and AI agents (or any x402-aware client) can pay for it automatically — no new infrastructure to run, no funds ever pass through the Global Commerce Index.

Install

npm install @korateams/x402-sdk

Usage

import express from 'express';
import { x402PaymentMiddleware } from '@korateams/x402-sdk';

const app = express();

app.get(
  '/premium-data',
  x402PaymentMiddleware({
    payTo: '0xYourRegisteredWalletAddress',
    price: '10000', // USDC has 6 decimals — this is $0.01
    description: 'Live NGN/USD exchange rates, updated every minute.',
    // Optional — lets the registry log real production transactions against
    // your endpoint, independently verified on-chain (Phase 10's strongest
    // self-reported tier). Get the endpoint id and secret from the registry
    // dashboard after registering this endpoint there.
    registryApiUrl: 'https://kora.dev/api/v1',
    registryEndpointId: 'your-endpoint-id-from-the-registry',
    registryFulfillmentSecret: 'your-endpoint-fulfillment-secret-from-the-registry',
  }),
  (req, res) => {
    // Only reached after a real, settled payment.
    res.json({ rate: 1234.5 });
  },
);

app.listen(3000);

How it works

1. A request arrives with no X-PAYMENT header → you respond 402 with your price (this middleware does that for you).
2. The client (an agent, wallet, or the registry's own probe) signs a payment authorization and retries with X-PAYMENT set.
3. This middleware verifies and settles the payment against the facilitator, sets X-PAYMENT-RESPONSE, and only then calls next() — your route handler never runs for an unpaid request.

Defaults to Coinbase's public facilitator and USDC on Base, matching the index's v1 target chain. Override network, asset, and facilitatorUrl if you need something else.

Registration

This middleware makes you machine-payable; it doesn't register you with the Global Commerce Index. Claim your entity and register your endpoint there first — see the main repository for the claim flow.