Express Checkout Example

This example demonstrates how a merchant backend can accept intentMandate (SD-JWT-VC) tokens from an agent and process a payment via the Delegare SDK. The source code is available in the examples/express-checkout directory of the Delegare repository.

Overview

Setup Buyer: The merchant creates a setup session for the user.
Authorization: The user completes the setup via the Delegare UI, generating an Intent Mandate.
Checkout: The AI agent sends the Intent Mandate to the merchant’s /api/checkout endpoint.
Execution: The merchant backend uses @delegare/sdk to charge the mandate.

Merchant Backend (Node.js)

const { Delegare } = require('@delegare/sdk');
const express = require('express');

const delegare = new Delegare({
  merchantId: process.env.DELEGARE_MERCHANT_ID,
  apiKey: process.env.DELEGARE_API_KEY,
  baseUrl: 'https://api.sandbox.delegare.dev/v1'
});

const app = express();
app.use(express.json());

app.post('/api/checkout', async (req, res) => {
  const { intentMandate, item } = req.body;

  try {
    // 1. Charge the agent!
    const receipt = await delegare.charge({
      intentMandate,
      amountCents: 1500, // $15.00
      currency: 'usd',
      description: `Order: ${item}`,
      idempotencyKey: `order_${Date.now()}`
    });

    res.json({ success: true, receipt });
  } catch (error) {
    res.status(402).json({ error: error.message });
  }
});

app.listen(4000);

Running the Demo locally

If you have the Delegare repository cloned, you can run the interactive demo:

cd examples/express-checkout
pnpm install
# Follow instructions in README to set your .env
pnpm start

Then, in a separate terminal, run the buyer setup script:

node setup-buyer.js

This script will give you a setup URL. Open it, complete the flow in Sandbox mode, and the script will automatically output a curl command you can use to test the checkout!

Testing the x402 API Paywall

This example also demonstrates the @delegare/x402 middleware, which automatically protects the /api/premium-data endpoint and charges AI agents $0.05 per request.

⚠️ IMPORTANT: x402 requires Crypto (USDC) The x402 protocol settles natively on-chain. To test this flow, your “Buyer” account MUST have a Crypto Wallet connected.

Ensure you are testing from a separate “Buyer” account (not your Merchant account). Use an incognito window if necessary.

Ensure that Buyer account has connected a Coinbase Smart Wallet (or similar) loaded with testnet USDC and ETH on Base Sepolia.

When you run node setup-buyer.js to generate the mandate, you must authorize the Crypto spending option, which will require you to actively sign a transaction on the Sepolia blockchain in your wallet. (A Fiat-only mandate will fail the x402 check!)

You can test this flow locally using the provided x402.js script! Simply add your Crypto-authorized mandate token to your .env file:

DELEGARE_MANDATE=eyJhbGci...

Then run the script:

pnpm x402

The script uses delegare.fetch() to automatically detect the 402 Payment Required challenge, authorize the $0.05 USDC payment via the Delegare SDK, and retry the request to securely fetch the premium data!

💡 Note on Dashboard Tracking: If you provide a raw 0x address in MERCHANT_USDC_WALLET inside your .env that is not connected to your Merchant profile, the payment will succeed on-chain, but the Delegare backend won’t know it belongs to you! It will be recorded under a generic “Web3 Merchant” and won’t appear in your dashboard. To see x402 transactions in your dashboard, make sure you connect that exact USDC wallet via the Payment Methods tab first.

​Overview

​Merchant Backend (Node.js)

​Running the Demo locally

​Testing the x402 API Paywall

Overview

Merchant Backend (Node.js)

Running the Demo locally

Testing the x402 API Paywall