Quickstart for Sellers

This guide walks you through integrating with x402 to enable payments for your API or service. By the end, your API will be able to charge buyers and AI agents for access.

Prerequisites

Before you begin, ensure you have:

• A crypto wallet to receive funds (any EVM-compatible wallet)
• Node.js and npm (or Python and pip) installed
• An existing API or server

Note

There are pre-configured examples available in the Coinbase repo for Node.js. There is also an advanced example that shows how to use the x402 SDKs to build a more complex payment flow. The following example shows how to adapt these for Polygon.

1. Install Dependencies

Install the x402 Express middleware package.

npm install x402-express

Install the x402 Next.js middleware package.

npm install x402-next

npm install x402-hono

2. Add Payment Middleware

Integrate the payment middleware into your application. You will need to provide:

• The Facilitator URL or facilitator object. For testing, use https://facilitator.x402.rs/ which works on Polygon Mainnet and Amoy.
• For a facilitator access on Polygon, please contact us here.
• The routes you want to protect.
• Your receiving wallet address.

Full example in the repo here.

import express from "express";
import { paymentMiddleware } from "x402-express";

const app = express();

app.use(paymentMiddleware(
  "0xCA3953e536bDA86D1F152eEfA8aC7b0C82b6eC00", // receiving wallet address
  {  // Route configurations for protected endpoints
    "GET /weather": {
      // USDC amount in dollars
      price: "$0.001",
      network: "polygon-amoy",
      // Optional: Add metadata for better discovery in x402 Bazaar
      config: {
        description: "Get current weather data for any location",
        inputSchema: {
          type: "object",
          properties: {
            location: { type: "string", description: "City name" }
          }
        },
        outputSchema: {
          type: "object",
          properties: {
            weather: { type: "string" },
            temperature: { type: "number" }
          }
        }
      }
    },
  },
  {
    url: process.env.FACILITATOR_URL || "https://facilitator.x402.rs", // Polygon Amoy facilitator
  }
));

// Implement your route
app.get("/weather", (req, res) => {
  res.send({
    report: {
      weather: "sunny",
      temperature: 70,
    },
  });
});

app.listen(4021, () => {
  console.log(`Server listening at http://localhost:4021`);
}); 

Full example in the repo here. Since this is a fullstack example, we recommend using the example to build this yourself, and treat the code snippet below as a reference to adapt for Polygon.

import { paymentMiddleware, Network } from 'x402-next';

// Configure the payment middleware
export const middleware = paymentMiddleware(
  "0xYourAddress", // your receiving wallet address 
  {  // Route configurations for protected endpoints
    '/protected': {
      price: '$0.01',
      network: "polygon-amoy",
      config: {
        description: 'Access to protected content'
      }
    },
  }
  {
    url: "https://facilitator.x402.rs/", // Facilitator URL for Polygon testnet and mainnet
  }
);

// Configure which paths the middleware should run on
export const config = {
  matcher: [
    '/protected/:path*',
  ]
};

import { Hono } from "hono";
import { paymentMiddleware, Network } from "x402-hono";

const app = new Hono();

// Configure the payment middleware
app.use(paymentMiddleware(
  "0xYourAddress",
  {
    "/protected-route": {
      price: "$0.01",
      network: "polygon-amoy",
      config: {
        description: "Access to premium content",
      }
    }
  },
  {
    url: 'https://facilitator.x402.rs' // 👈 Facilitator URL
  }
));

// Implement your route
app.get("/protected-route", (c) => {
  return c.json({ message: "This content is behind a paywall" });
});

serve({
  fetch: app.fetch,
  port: 3000
});