Quickstart

Build your first monetized API in 5 minutes.

mkdir my-monetized-api
cd my-monetized-api
npm init -y
npm install express @xapi-fi/sdk

Create index.js:

const express = require('express');
const XAPIFi = require('@xapi-fi/sdk/server');

const app = express();
const xapi = new XAPIFi({
  apiKey: process.env.XAPI_FI_KEY
});

app.use(express.json());

app.post('/api/generate',
  xapi.protect({ price: 0.001 }),
  async (req, res) => {
    res.json({
      message: 'Success!',
      prompt: req.body.prompt
    });
  }
);

app.listen(3000, () => {
  console.log('Server running on port 3000');
});

XAPI_FI_KEY=your_key_here node index.js

You've created a monetized API endpoint that:

• ▹Requires 0.001 USD payment per call
• ▹Uses the x402 payment protocol
• ▹Automatically verifies payments via the x-payment header
• ▹Works with any Web3 wallet

When a client calls your endpoint:

1. ▹First request returns 402 Payment Required with payment details
2. ▹Client's wallet creates and signs a payment transaction
3. ▹Client retries request with x-payment header containing the payment proof
4. ▹Your endpoint verifies the payment and processes the request

• ▹Add more endpoints with different pricing
• ▹Implement dynamic pricing based on request parameters
• ▹Add analytics tracking to monitor revenue
• ▹Deploy to production