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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 a custom ERC-7710 scheme that routes verification and settlement through the MetaMask facilitator.

Prerequisites​

Steps​

1. Install the dependencies​

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

2. Create the ERC-7710 scheme​

Create a custom scheme that extends ExactEvmScheme from @x402/evm to add ERC-7710 delegation support.

The scheme overrides enhancePaymentRequirements to set assetTransferMethod to erc7710 and include the facilitator addresses so buyers can scope their delegation to a specific set of facilitators before creating the payment payload.

import { ExactEvmScheme } from '@x402/evm/exact/server'
import type { PaymentRequirements, SupportedKind } from '@x402/core/types'
import type { FacilitatorClient } from '@x402/core/server'

export class Erc7710ExactEvmScheme extends ExactEvmScheme {
  constructor(private readonly facilitatorClient: FacilitatorClient) {
    super()
  }

  async enhancePaymentRequirements(
    paymentRequirements: PaymentRequirements,
    supportedKind: SupportedKind,
    facilitatorExtensions: string[]
  ): Promise<PaymentRequirements> {
    const enhanced = await super.enhancePaymentRequirements(
      paymentRequirements,
      supportedKind,
      facilitatorExtensions
    )

    const supported = await this.facilitatorClient.getSupported()
    const facilitators = [
      ...(supported.signers[paymentRequirements.network] ?? []),
      ...(supported.signers['eip155:*'] ?? []),
    ]

    return {
      ...enhanced,
      extra: {
        ...enhanced.extra,
        assetTransferMethod: 'erc7710',
        facilitators,
      },
    }
  }
}

3. Configure the server​

Set up the Express server with the x402 paymentMiddleware and the custom ERC-7710 scheme. 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 mainnet. Replace the payout address in src/config.ts with your own seller wallet address.

import express, { type Request, type Response } from 'express'
import cors from 'cors'
import { paymentMiddleware } from '@x402/express'
import { x402ResourceServer } from '@x402/core/server'
import { Erc7710ExactEvmScheme } from './scheme.js'
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,
          },
        ],
        description: 'Access to protected resource',
        mimeType: 'application/json',
      },
    },
    new x402ResourceServer(facilitatorClient).register(
      NETWORK_ID,
      new Erc7710ExactEvmScheme(facilitatorClient)
    )
  )
)

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

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

Next steps​

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