Create an x402 server with ERC-7710

In this guide, you build a Node.js server that charges for HTTP API access using x402 and accepts ERC-7710 delegation payments verified through the MetaMask facilitator.

You use the official @x402/express middleware with the @metamask/x402 package, which provides an ERC-7710 server scheme that routes verification and settlement through the MetaMask facilitator.

Prerequisites

• Node.js 18 or later.
• A Node.js Express server.
• A seller payout address to receive funds (for example, a MetaMask wallet address).

Facilitator URLs

The following table lists the available MetaMask facilitator endpoints:

Name	ID	URL
Base	eip155:8453	https://tx-sentinel-base-mainnet.api.cx.metamask.io/platform/v2/x402
Base Sepolia	eip155:84532	https://tx-sentinel-base-sepolia.api.cx.metamask.io/platform/v2/x402
Monad	eip155:143	https://tx-sentinel-monad-mainnet.api.cx.metamask.io/platform/v2/x402

Steps

1. Install the dependencies

npm

npm install @metamask/x402 @x402/core @x402/express cors express

Yarn

yarn add @metamask/x402 @x402/core @x402/express cors express

pnpm

pnpm add @metamask/x402 @x402/core @x402/express cors express

Bun

bun add @metamask/x402 @x402/core @x402/express cors express

2. Configure middleware

Set up the Express server with the x402 paymentMiddleware and the x402ExactEvmErc7710ServerScheme from @metamask/x402. The scheme automatically adds payment requirements with ERC-7710 fields when assetTransferMethod is set to erc7710 in the route configuration.

The paymentMiddleware intercepts requests to protected routes and handles the full x402 payment flow, including requirements advertisement, verification, and settlement.

In this example, you create a protected GET /api/hello endpoint that charges 0.01 USDC on Base Sepolia. Replace the payout address in src/config.ts with your own seller wallet address.

src/index.ts

import express, { type Request, type Response } from 'express'
import cors from 'cors'
import { paymentMiddleware, x402ResourceServer } from '@x402/express'
import { x402ExactEvmErc7710ServerScheme } from '@metamask/x402'
import { NETWORK_ID, PORT, payToAddress, facilitatorClient } from './config.js'

const app = express()
app.use(cors({ exposedHeaders: ['PAYMENT-REQUIRED', 'PAYMENT-RESPONSE'] }))

app.use(
  paymentMiddleware(
    {
      'GET /api/hello': {
        accepts: [
          {
            scheme: 'exact',
            price: '$0.01',
            network: NETWORK_ID,
            payTo: payToAddress,
            extra: {
              assetTransferMethod: 'erc7710',
            },
          },
        ],
        description: 'Access to protected resource',
        mimeType: 'application/json',
      },
    },
    new x402ResourceServer(facilitatorClient).register(
      NETWORK_ID,
      new x402ExactEvmErc7710ServerScheme()
    )
  )
)

app.get('/api/hello', (_req: Request, res: Response) => {
  res.json({ message: 'Hello!' })
})

app.listen(PORT, () => {
  console.log(`[seller] Server running on http://localhost:${PORT}`)
})

src/config.ts

import { HTTPFacilitatorClient } from '@x402/core/server'

export const NETWORK_ID = 'eip155:84532'
export const PORT = 4402

// Replace with your seller payout address.
export const payToAddress = '0x<PAY_TO_ADDRESS>'

// MetaMask facilitator base URL for x402 on Base Sepolia.
export const facilitatorClient = new HTTPFacilitatorClient({
  url: 'https://tx-sentinel-base-sepolia.api.cx.metamask.io/platform/v2/x402',
})

Next steps

• Learn more about ERC-7710 delegation.
• See the x402 ERC-7710 specification.