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This guide shows how to make x402 payments from the buyer’s perspective. Use the x402 SDK to handle payment flows, interact with paywalled resources, and process 402 Payment Required responses.

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Prerequisites

  • Node.js and npm installed
  • A SKALE Chain endpoint
  • Understanding of x402 protocol
  • Familiarity with TypeScript/JavaScript

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Overview

To buy with x402, you need to:
  1. Install the x402 SDK
  2. Handle 402 Payment Required responses
  3. Create and settle payments
  4. Retry requests with payment headers

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Quick Start

Install the x402 SDK: 
npm install @coinbase/x402-sdk

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Basic Payment Flow

Here’s how to make a payment to access a paywalled resource: 
import { X402Client } from '@coinbase/x402-sdk';
import { ethers } from 'ethers';

const provider = new ethers.JsonRpcProvider('YOUR_SKALE_RPC_URL');
const wallet = new ethers.Wallet(PRIVATE_KEY, provider);

const x402Client = new X402Client({
  wallet: wallet,
  facilitatorURL: 'https://facilitator.dirtroad.dev',
});

async function accessPaywalledResource(url: string) {
  const response = await fetch(url);
  
  if (response.status === 402) {
    const paymentInfo = await response.json();
    const payment = await x402Client.createPayment(paymentInfo);
    await x402Client.settle(payment);
    
    const retryResponse = await fetch(url, {
      headers: {
        'X-PAYMENT': JSON.stringify(payment),
      },
    });
    
    return await retryResponse.json();
  }
  
  return await response.json();
}

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Using @faremeter/fetch

The Faremeter fetch wrapper automatically handles 402 responses: 
import { createX402Fetch } from '@faremeter/fetch';
import { ethers } from 'ethers';

const provider = new ethers.JsonRpcProvider('YOUR_SKALE_RPC_URL');
const wallet = new ethers.Wallet(PRIVATE_KEY, provider);

const x402Fetch = createX402Fetch({
  wallet: wallet,
  facilitatorURL: 'https://facilitator.dirtroad.dev',
});

// Automatically handles 402 responses
const data = await x402Fetch('https://api.example.com/premium-data');

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Payment Options

Handle multiple payment options: 
async function accessResourceWithOptions(url: string) {
  const response = await fetch(url);
  
  if (response.status === 402) {
    const paymentInfo = await response.json();
    const selectedOption = paymentInfo.accepts[0];
    
    const payment = await x402Client.createPayment({
      ...selectedOption,
      resource: url,
    });
    
    await x402Client.settle(payment);
    
    const retryResponse = await fetch(url, {
      headers: {
        'X-PAYMENT': JSON.stringify(payment),
      },
    });
    
    return await retryResponse.json();
  }
  
  return await response.json();
}

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Error Handling

async function accessResource(url: string) {
  const response = await fetch(url);
  
  if (response.status === 402) {
    const paymentInfo = await response.json();
    const payment = await x402Client.createPayment(paymentInfo);
    await x402Client.settle(payment);
    
    const retryResponse = await fetch(url, {
      headers: {
        'X-PAYMENT': JSON.stringify(payment),
      },
    });
    
    if (retryResponse.status === 402) {
      throw new Error('Payment settlement failed');
    }
    
    return await retryResponse.json();
  }
  
  return await response.json();
}

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Next Steps

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Resources