xrail.io: Pay-As-You-Go Facilitation for x402 Transactions

Sending transactions on-chain can be complex, expensive, and full of friction. Users often face high upfront costs, slow onboarding, and limited visibility into execution. xRail was created to solve these problems offering a simple, scalable, and transparent pay-as-you-go solution for transactions executed through the x402 protocol.

Imagine you’re running an AI agent that makes 100 on-chain calls a day. Paying for each call individually with a native wallet is slow, confusing, and expensive. What if you could preload credits and spend them seamlessly whenever your agent needs to transact?

This is exactly the kind of friction xRail removes. Sending on-chain transactions shouldn’t be a headache, but for many developers and teams using x402, it is high upfront costs, confusing onboarding, and unpredictable execution fees make managing payments a challenge.

That’s why we built xrail.io: a pay-as-you-go facilitator that makes sending x402 transactions simple, predictable, and transparent.

What is xRail?

xRail offers a facilitator for x402 transactions that lets users pay only for the execution they actually use. Using a credit-based system built on the x402 protocol, xRail allows transactions from AI agent operations to backend services to run seamlessly while keeping costs predictable and transparen

Key advantages:

• x402-native credits - purchase and manage execution credits directly via the x402 protocol.
• Protocol-compatible - built on top of x402 without modifying it in any way.
• Low upfront costs - no need to lock large amounts of funds.
• Easy integration - simple SDK/API to start sending transactions.
• Transparent execution - monitor activity and credit usage in real-time.

Why Current Solutions Fall Short

• Traditional facilitator models often struggle with scalability and cost predictability:
• Zero-fee facilitators may not be sustainable for small projects.
• Onboarding and managing transactions can be cumbersome.
• Users lack clear visibility of execution costs.

xRail addresses all of these pain points with flexible pay-as-you-go credits and a user-friendly interface all while remaining fully compatible with the x402 protocol.

How It Works

1. Buy credits via x402: Anyone can purchase credits based on expected transaction activity, using the x402 protocol.
2. Send transactions: Transactions are executed using the purchased credits.
3. Monitor usage: Track credit consumption and execution performance in real-time.

Integration Example Using @payrail/sdk-nodejs

xRail supports seamless integration using the official Node.js SDK. The SDK handles 402 Payment Required responses, verifies payments, and settles transactions through your facilitator automatically:

import axios from 'axios';
import { PayRail } from '@payrail/sdk-nodejs';
import dotenv from 'dotenv';

dotenv.config();

// Initialize PayRail with your facilitator URL and private key
const payrail = new PayRail({
  facilitatorUrl: process.env.FACILITATOR_URL,
  privateKey: process.env.PRIVATE_KEY,
  debug: true,
});

// Create an axios client for the target service
const apiClient = axios.create({
  baseURL: 'https://paid-api.example.com',
});

// Attach PayRail interceptor to handle 402 responses automatically
payrail.attachInterceptor(apiClient);

// Example call — if the endpoint demands payment, PayRail will settle it
(async () => {
  try {
    const response = await apiClient.get('/paid-endpoint');
    console.log('Success response:', response.data);
  } catch (error) {
    console.error('Request failed:', error);
  }
})();

This workflow allows users to focus on executing transactions rather than manually handling x402 payments. Developers and services alike can also access the facilitator client for full control over supported networks, payment headers, and settlement operations.

Benefits of Using xRail

• Predictable costs: Pay only for the transactions you execute.
• Fully compatible with x402: No protocol changes required.
• Scalable for any type of transaction: From AI agent operations to backend services using facilitators.
• User-friendly: Quick setup, clear SDK/API, and real-time monitoring.

Get Started

Experience the simplicity of xRail using our demo

The Future of Facilitated x402 Transactions

xrail.io is more than just a facilitator, it’s a new economic model for transaction execution on x402. By making execution costs predictable and transparent, while remaining fully x402-compatible, we empower users to innovate without worrying about complex blockchain interactions or hidden fees.