Developer Resources

Everything you need to build with {xpay✦} and the x402 protocol. From SDKs and code examples to testing tools and open source projects.

SDKs & Libraries

Official {xpay✦} SDKs

Package	Description	Install
`@xpaysh/agent-kit`	Complete toolkit for agent developers	`npm install @xpaysh/agent-kit`
`@xpaysh/agent-kit`	Agent spending protection	`npm install @xpaysh/agent-kit`
`@xpaysh/agent-kit`	API monetization tools	`npm install @xpaysh/agent-kit`
`@xpaysh/explorer`	Transaction monitoring	`npm install @xpaysh/explorer`
`@xpaysh/sdk`	Core x402 utilities	`npm install @xpaysh/sdk`

x402 Protocol SDKs

Language	Package	Description
TypeScript	`@x402/sdk`	Official TypeScript SDK
Python	`x402-python`	Python implementation
Go	`x402-go`	Go implementation
Rust	`x402-rust`	Rust implementation

Code Examples

Quick Start Examples


// Agent with spending limits
import { SmartProxy } from '@xpaysh/agent-kit'
 
const smartProxy = new SmartProxy({
  maxDailySpend: 100,
  maxPerRequest: 5
})
 
const response = await smartProxy.protectedFetch('https://api.openai.com/v1/chat/completions', {
  method: 'POST',
  body: JSON.stringify({
    model: 'gpt-4',
    messages: [{ role: 'user', content: 'Hello' }]
  })
})


// API monetization
import { XpayPaywall } from '@xpaysh/agent-kit'
import express from 'express'
 
const app = express()
const paywall = new Paywall({
  pricePerRequest: 0.10,
  receivingWallet: '0x...'
})
 
app.get('/api/premium', paywall.middleware, (req, res) => {
  res.json({ data: 'Premium content' })
})

Framework Integrations

Next.js


// pages/api/protected.ts
import { NextApiRequest, NextApiResponse } from 'next'
import { XpayPaywall } from '@xpaysh/agent-kit'
 
const paywall = new Paywall({
  pricePerRequest: 0.05,
  receivingWallet: process.env.RECEIVING_WALLET
})
 
export default async function handler(req: NextApiRequest, res: NextApiResponse) {
  const paymentResult = await paywall.verifyPayment(req)
  
  if (!paymentResult.success) {
    return res.status(402).json({
      error: 'Payment required',
      payment: paymentResult.paymentInstructions
    })
  }
  
  res.json({ message: 'Access granted' })
}

LangChain


import { ChatOpenAI } from 'langchain/chat_models/openai'
import { SmartProxy } from '@xpaysh/agent-kit'
 
const smartProxy = new SmartProxy({
  maxDailySpend: 50,
  agentId: 'langchain-agent'
})
 
const chat = new ChatOpenAI({
  openAIApiKey: process.env.OPENAI_API_KEY,
  configuration: {
    fetch: smartProxy.protectedFetch.bind(smartProxy)
  }
})

Vercel Edge Functions


import { NextRequest } from 'next/server'
import { XpayPaywall } from '@xpaysh/agent-kit'
 
export const config = {
  runtime: 'edge'
}
 
const paywall = new Paywall({
  pricePerRequest: 0.01,
  receivingWallet: process.env.RECEIVING_WALLET
})
 
export default async function handler(req: NextRequest) {
  return await paywall.handleEdgeRequest(req)
}

Open Source Projects

{xpay✦} actively contributes to the x402 ecosystem with open source tools:

Core Projects

awesome-x402

Curated list of x402 resources

Protocol documentation and tutorials
SDK implementations in multiple languages
Real-world examples and case studies
Community tools and resources

x402-agent-kit

Build x402-paying agents in 5 minutes

Sample LangChain agent with x402 payments
Mock x402-protected API for testing
Docker compose for instant local development
Integration guides for popular agent frameworks

x402-local

Local x402 development environment

npx x402-local for instant setup
Local facilitator simulation
CLI for generating test wallets
Browser extension for payment injection

x402-sdk

TypeScript-first x402 SDK

Zero-dependency implementation
Full TypeScript types
React hooks for x402 payments
Excellent documentation and examples

Development Tools

CLI Tools

{xpay✦} CLI


# Install globally
npm install -g @xpaysh/cli
 
# Create new smart proxy
xpaysh smart-proxy create --name "my-agents"
 
# Configure agent limits
xpay agent configure my-bot --max-daily 100 --max-request 5
 
# Monitor spending
xpay monitor --agent my-bot --live

x402 Local Development


# Start local x402 environment
npx x402-local start
 
# Generate test wallets with funds
npx x402-local wallet create --fund 100
 
# Mock API with x402 protection
npx x402-local mock-api --price 0.05 --port 3001

Browser Extensions

{xpay✦} DevTools

Browser extension for debugging x402 payments:

Monitor payment flows in real-time
Inspect payment instructions and responses
Test payment scenarios without real funds
Debug agent spending patterns

Testing Tools

Payment Simulation


import { MockX402Server } from '@xpaysh/agent-kit-testing'
 
const mockServer = new MockX402Server({
  port: 3001,
  price: 0.05,
  currency: 'USDC'
})
 
await mockServer.start()
 
// Test your agent against mock API
const response = await agent.callAPI('http://localhost:3001/api/test')

Spending Simulation


import { SpendingSimulator } from '@xpaysh/agent-kit-testing'
 
const simulator = new SpendingSimulator({
  agent: 'test-agent',
  maxDailySpend: 100
})
 
// Simulate various spending patterns
await simulator.simulatePattern('steady', { requestsPerHour: 10 })
await simulator.simulatePattern('burst', { peakRequestsPerSecond: 5 })
await simulator.simulatePattern('random', { averageRequestsPerMinute: 2 })

Testing & Debugging

Test Networks

Network	Purpose	USDC Contract	Faucet
Base Sepolia	Testing	`0x036CbD53842c5426634e7929541eC2318f3dCF7e`	Circle Faucet
Ethereum Sepolia	Testing	`0x1c7D4B196Cb0C7B01d743Fbc6116a902379C7238`	Circle Faucet
Polygon Amoy	Testing	`0x41e94eb019c0762f9bfcf9fb1e58725bfb0e7582`	Circle Faucet

Debugging Common Issues

Payment Verification Failures


import { X402Debug } from '@xpaysh/sdk'
 
const debug = new X402Debug({
  facilitator: 'https://facilitator.base.org',
  network: 'base-sepolia'
})
 
// Debug payment verification
const result = await debug.verifyPayment('payment_123')
console.log('Payment status:', result.status)
console.log('Failure reason:', result.failureReason)
console.log('Transaction hash:', result.txHash)

Agent Spending Analysis


import { XpayAnalytics } from '@xpaysh/agent-kit'
 
const analytics = new XpayAnalytics({
  apiKey: process.env.XPAY_API_KEY
})
 
// Analyze agent spending patterns
const report = await analytics.analyzeAgent('my-bot', {
  timeframe: '7d',
  includeFailures: true
})
 
console.log('Total spend:', report.totalSpend)
console.log('Average per request:', report.averagePerRequest)
console.log('Failure rate:', report.failureRate)

API References

REST APIs

{xpay✦} API Reference - Complete API documentation
x402 Facilitator API - Coinbase facilitator API
Base Network API - Base blockchain API

WebSocket APIs


import { XpayWebSocket } from '@xpaysh/agent-kit'
 
const ws = new XpayWebSocket({
  apiKey: process.env.XPAY_API_KEY,
  projectId: 'proj_123'
})
 
// Real-time agent spending updates
ws.subscribe('agent.spending', (event) => {
  console.log('Agent spending update:', event)
})

Community Resources

Discord Channels

Join our Discord server for real-time help:

#general - General discussion
#developer-help - Get help with integration
#agent-dev - Agent development discussion
#api-monetization - API provider discussion
#showcase - Show off your projects

GitHub Discussions

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