x402 Agent SDK

Transform any API into an x402 payment-enabled API in minutes. Built for AI agents and autonomous systems.

Why x402?

The HTTP 402 "Payment Required" status code has been unused for 30 years. x402 finally puts it to work, enabling:

Agent-to-Agent Payments: AI agents can autonomously pay for API access
Micropayments: Pay per request, no subscriptions required
No Accounts: Cryptographic wallet-based authentication
Multi-Chain: Support for EVM, Solana, and Stacks

Features

🌐 Multi-Chain Support: Ethereum, Polygon, Base, Arbitrum, Optimism, Avalanche, BSC, Celo, Solana, Stacks, Tempo
⚡ Tempo.xyz Integration: Stripe-backed blockchain with Machine Payments Protocol (MPP)
⚡ Lightning Network: Bitcoin Lightning Network support for micropayments (LND, Core Lightning, LNURL)
🔐 W3C Verifiable Credentials: Built-in credential generation for agent identity
🛡️ Security First: Input validation, rate limiting, address sanitization, ECDSA signing
⚡ Fast: Rust core with WASM bindings for browser/Node.js
🔌 Framework Adapters: Express, Fastify, Next.js, Axum, Django, Flask, Gin, Fiber, Spring Boot
🛒 Platform Adapters: Shopify, WordPress plugins
💳 Payment Facilitators: Stripe, Coinbase Commerce, Tempo.xyz
📦 TypeScript: Full type definitions included
💳 MPP Sessions: OAuth for money - pre-authorize spending caps for AI agents

Quick Start

Rust

# Cargo.toml
[dependencies]
x402-agent-sdk = "0.1"

use x402_agent_sdk::{
    AgentServer,
    EvmNetwork,
    EvmPayment,
    EvmToken,
};

let server = AgentServer::new(
    100,                      // price per request
    "v1-eip155-exact",       // payment scheme
    "eip155:1",             // network (Ethereum)
    "USDC",                 // payment token
    "0x742d...",           // recipient address
);

// Create payment requirement
let pr = server.create_payment_required(Some("Premium API Access"));

TypeScript / Deno

import { X402Server, X402Client } from "https://deno.land/x/x402/mod.ts";

// Server
const server = new X402Server(
  100,
  "v1-eip155-exact",
  "eip155:1",
  "USDC",
  "0x742d..."
);

// Client
const client = new X402Client({
  facilitatorUrl: "https://facilitator.x402.rs"
});

const response = await client.request("https://api.example.com/data");

Node.js / Browser (WASM)

import init, { WasmPaymentRequired } from 'x402-agent-sdk';

await init();

const pr = new WasmPaymentRequired(
  "v1-eip155-exact",
  "eip155:1",
  "USDC",
  "100",
  "0x742d..."
);

Supported Blockchains

EVM Chains

Chain	Chain ID	Native Token	USDC Address
Ethereum	1	ETH	0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48
Polygon	137	MATIC	0x2791Bca1f2de4661ED88A30C99A7a9449Aa84174
Base	8453	ETH	0x833589fCD6eDb6E08f4c7C32D4f71B54bdA02913
Arbitrum	42161	ETH	0xaf88d065e77c8cC2239327C5EDb3A432268e5831
Optimism	10	ETH	0x0b2C639c533813f4Aa9D7837CAf62653d097Ff85
Avalanche	43114	AVAX	0xB97EF9Ef8734C71904D8002F8b6Bc66Dd9c48a6E
BSC	56	BNB	0x8AC76a51cc950d9822D68b83fE1Ad97B32Cd580d

Solana

Network	Chain ID	Token Address
Mainnet	101	EPjFWdd5AufqSSFqM7BcEgHwgsn7kWGLelwTjB9mFLAQ (USDC)
Devnet	102	-
Testnet	103	-

Stacks

Network	Chain ID	Token
Mainnet	0x01	STX
Testnet	0x80000000	STX

Tempo (Stripe + Paradigm)

Network	Chain ID	Features
Mainnet	5000	Stripe integration, MPP Sessions
Testnet	5001	Testing
Devnet	5002	Local development

Tempo is Stripe and Paradigm's blockchain for payments:

Native Stripe integration (accept fiat + crypto)
Machine Payments Protocol (MPP) for AI agents
Sessions: Pre-authorize spending caps for streaming payments
100K TPS, sub-second finality

Framework Integration

Express.js

import express from "express";
import { x402Middleware } from "x402-agent-sdk/adapters/express";

const app = express();

app.use(x402Middleware({
  pricePerRequest: 100,
  scheme: "v1-eip155-exact",
  network: "eip155:1",
  paymentToken: "0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48",
  recipient: "0x742d35Cc6634C0532925a3b844Bc9e7595f0fB1E"
}));

app.get("/api/data", (req, res) => {
  res.json({ data: "Paid content!" });
});

Fastify

import Fastify from "fastify";
import { x402Plugin } from "x402-agent-sdk/adapters/fastify";

const fastify = Fastify();

await fastify.register(x402Plugin, {
  pricePerRequest: 100,
  scheme: "v1-eip155-exact",
  network: "eip155:1",
  paymentToken: "0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48",
  recipient: "0x742d35Cc6634C0532925a3b844Bc9e7595f0fB1E"
});

Next.js

// middleware.ts
import { x402Middleware } from "x402-agent-sdk/adapters/nextjs";

export function middleware(request: NextRequest) {
  return x402Middleware({
    pricePerRequest: 100,
    scheme: "v1-eip155-exact",
    network: "eip155:1",
    paymentToken: "0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48",
    recipient: "0x742d35Cc6634C0532925a3b844Bc9e7595f0fB1E"
  })(request);
}

Axum (Rust)

use x402_agent_sdk::adapters::axum::{x402_middleware, AxumX402Config};

let config = AxumX402Config::new(
    100,
    "v1-eip155-exact",
    "eip155:1",
    "0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48",
    "0x742d..."
).with_description("API Access");

Router::new()
    .route("/api/data", get(handler))
    .layer(middleware::from_fn(move |req, next| {
        x402_middleware(config.clone(), req, next)
    }));

Python

FastAPI

from x402_fastapi import X402Middleware, X402Config

config = X402Config(
    price_per_request=100,
    network="eip155:1",
    payment_token="0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48",
    recipient="0x742d35Cc6634C0532925a3b844Bc9e7595f0fB1E"
)

app = FastAPI()
app.add_middleware(X402Middleware, config=config)

Flask

from x402_flask import X402, X402Config

x402 = X402(app, config=X402Config(
    price_per_request=100,
    network="eip155:1",
    payment_token="0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48",
    recipient="0x742d35Cc6634C0532925a3b844Bc9e7595f0fB1E"
))

Django

# settings.py
MIDDLEWARE = [
    'x402_django.X402Middleware',
]

X402_CONFIG = {
    'price_per_request': 100,
    'network': 'eip155:1',
    'payment_token': '0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48',
    'recipient': '0x742d35Cc6634C0532925a3b844Bc9e7595f0fB1E',
}

Go

Gin

import "x402/adapters/go/gin"

router.Use(gin.Middleware(gin.Config{
    PricePerRequest: 100,
    Network:        "eip155:1",
    PaymentToken:   "0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48",
    Recipient:      "0x742d35Cc6634C0532925a3b844Bc9e7595f0fB1E",
}))

Java

Spring Boot

@Configuration
public class X402Config {
    @Bean
    public X402Config x402Config() {
        X402Config config = new X402Config();
        config.setPricePerRequest(100);
        config.setNetwork("eip155:1");
        config.setPaymentToken("0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48");
        config.setRecipient("0x742d35Cc6634C0532925a3b844Bc9e7595f0fB1E");
        return config;
    }
}

C# /.NET

var builder = WebApplication.CreateBuilder(args);
builder.Services.AddX402(options => {
    options.PricePerRequest = 100;
    options.Network = "eip155:1";
    options.PaymentToken = "0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48";
    options.Recipient = "0x742d35Cc6634C0532925a3b844Bc9e7595f0fB1E";
});

Ruby

Rails

# Gemfile
gem 'x402_rails'

# config/initializers/x402.rb
Rails.application.config.x402.price_per_request = 100
Rails.application.config.x402.network = "eip155:1"
Rails.application.config.x402.payment_token = "0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48"
Rails.application.config.x402.recipient = "0x742d35Cc6634C0532925a3b844Bc9e7595f0fB1E"

PHP

Laravel

# app/Http/Kernel.php
protected $middleware = [
    \App\Http\Middleware\X402Middleware::class,
];

Platform Adapters

Shopify

import { x402Shopify } from "x402-agent-sdk/adapters/shopify";

const shopify = x402Shopify({
  shopDomain: "your-store.myshopify.com",
  accessToken: "your-access-token",
  pricePerRequest: 100,
  network: "eip155:1",
  paymentToken: "0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48",
});

WordPress

// In your WordPress plugin
add_action('init', function() {
    x402_init([
        'price_per_request' => 100,
        'network' => 'eip155:1',
        'payment_token' => '0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48',
        'recipient' => '0x742d35Cc6634C0532925a3b844Bc9e7595f0fB1E'
    ]);
});

Payment Facilitators

Stripe

import { StripeFacilitator } from "x402-agent-sdk/adapters/facilitator";

const stripe = new StripeFacilitator("sk_live_...");
const result = await stripe.verifyPayment({
  txHash: "pi_xxx",
  amount: "100",
  token: "usd",
  network: "stripe",
  recipient: "acct_xxx",
  from: "cus_xxx"
});

Tempo.xyz

import { TempoFacilitator } from "x402-agent-sdk/adapters/facilitator";

const tempo = new TempoFacilitator("tempo_api_key");
const session = await tempo.createPaymentLink({
  amount: "100",
  token: "USDC",
  recipient: "0x742d...",
  description: "API Access"
});

Bitcoin Lightning

import { createLightningAdapter } from "x402-agent-sdk/adapters/lightning";

const lightning = createLightningAdapter({
  nodeType: 'lnd',
  nodeUrl: 'https://localhost:8080',
  authToken: 'macaroon_hex'
});

const invoice = await lightning.createInvoice({
  amount: 1000,  // sats
  description: 'API Access',
  expirySeconds: 3600
});

Payment Flow

┌──────────┐    GET /data     ┌────────────┐
│  Agent   │ ───────────────▶ │   Server   │
└──────────┘                  └──────┬─────┘
                                     │
                              ┌──────▼──────┐
                              │ No Payment?  │
                              │  402 Response│
                              │ + PaymentReq │
                              └──────┬──────┘
                                     │
       ┌─────────────────────────────┘
       │ 1. Parse PaymentRequired
       │ 2. Fund Wallet
       │ 3. Sign Payment
       ▼
┌──────────┐   GET /data      ┌────────────┐
│  Agent   │ + X-Payment-Token │   Server   │
│          │ ────────────────▶ │            │
└──────────┘                  └──────┬─────┘
                                     │
                              ┌──────▼──────┐
                              │ Verify Token │
                              │  Return Data │
                              └──────────────┘

Security

use x402_agent_sdk::{InputValidator, RateLimiter, RateLimitConfig};

// Address validation
InputValidator::validate_address("0x742d...", "ethereum")?;  // ✅
InputValidator::validate_address("invalid", "ethereum")?;    // ❌

// Amount validation  
InputValidator::validate_amount("100")?;  // ✅
InputValidator::validate_amount("0")?;   // ❌

// Rate limiting
let limiter = RateLimiter::new(RateLimitConfig {
    max_requests: 100,
    window_seconds: 60,
});
limiter.check("user_address").await?;

Environment Variables

# Server
X402_ENABLED=true
X402_NETWORK=eip155:1
X402_PAYMENT_TOKEN=0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48
X402_RECIPIENT=0x742d35Cc6634C0532925a3b844Bc9e7595f0fB1E

# Client
X402_FACILITATOR_URL=https://facilitator.x402.rs

Development

# Build
cargo build

# Test
cargo test

# WASM Build
wasm-pack build --target web --out-dir pkg

# Documentation
cargo doc --open

Resources

License

MIT or Apache-2.0

Name		Name	Last commit message	Last commit date
Latest commit History 23 Commits
.github/workflows		.github/workflows
adapters		adapters
cli		cli
contracts		contracts
deno		deno
docs		docs
examples		examples
src		src
tweets		tweets
.gitignore		.gitignore
ARCHITECTURE.md		ARCHITECTURE.md
CHANGELOG.md		CHANGELOG.md
Cargo.lock		Cargo.lock
Cargo.toml		Cargo.toml
Dockerfile		Dockerfile
Dockerfile.demo		Dockerfile.demo
Dockerfile.frontend		Dockerfile.frontend
Makefile		Makefile
README.md		README.md
docker-compose.demo.yml		docker-compose.demo.yml

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x402 Agent SDK

Why x402?

Features

Quick Start

Rust

TypeScript / Deno

Node.js / Browser (WASM)

Supported Blockchains

EVM Chains

Solana

Stacks

Tempo (Stripe + Paradigm)

Framework Integration

Express.js

Fastify

Next.js

Axum (Rust)

Python

FastAPI

Flask

Django

Go

Gin

Java

Spring Boot

C# /.NET

Ruby

Rails

PHP

Laravel

Platform Adapters

Shopify

WordPress

Payment Facilitators

Stripe

Tempo.xyz

Bitcoin Lightning

Payment Flow

Security

Environment Variables

Development

Resources

License

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