Welcome to the Agentic Web

x402Relay is the Payment & Discovery Hub for AI Agents

x402Relay connects payment, discovery, and execution into one machine-native flow — so AI agents can find trusted APIs, settle instantly via HTTP 402, and operate autonomously at internet scale.

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agent-runtime

# AI agent discovers APIs from the Marketplace
GET /api/search?tags=translation&currency=USDC
→ 3 verified services found

# Agent picks the best one and calls it
POST https://translate.example.com/api/v1

# 402 Payment Required → Agent pays with USDC
HTTP/1.1 200 OK
Payment: settled | 0.001 USDC | tx: 0x3f...a1

For API Providers

Monetize your APIs for AI agents. x402 Gateway lets you add pay-per-call pricing with one line of config, and list on the Agent Marketplace instantly.

Explore Features

For Agent Builders

Give your AI agents payment superpowers. Integrate x402 payments with one SDK call so agents can autonomously discover, negotiate, and pay for APIs.

See How It Works

Quickstart

Go live in 5 minutes

Full Docs

1Install

npm install @x402relay/sdk

2Config

x402relay proxy --upstream localhost:3000 --price 0.001

3First paid call

curl https://your-api.com/endpoint
# HTTP 200 OK  Payment: settled | 0.001 USDC

Full Docs

The Problem

APIs Weren’t Built for AI Agents

Today’s API economy relies on human-centric authentication and billing. As AI agents become autonomous, this model breaks down.

API Keys Everywhere

Every API requires a unique key, separate registration, and manual management. AI agents can’t autonomously acquire new API access.

Billing Account Overhead

Credit cards, invoices, payment methods — each provider has its own billing system. Impossible for autonomous agents to navigate.

Manual Setup Required

Sign up, verify email, add payment method, generate keys, configure SDKs. A process designed for humans, not machines.

No Discovery

AI agents have no way to find new APIs on their own. Every service URL must be hardcoded by a human. The agentic economy can’t scale without autonomous discovery.

Protocol

How x402 Works

A simple, four-step HTTP flow that turns any API into a pay-per-use service — no API keys needed.

1

Request

Agent Calls API

AI agent sends a standard HTTP request to a paid API endpoint.

GET /api/translate

2

402

Payment Required

Server responds with HTTP 402 and payment requirements (amount, token, address).

402 Payment Required

3

Pay

Sign & Pay

Agent signs a USDC payment authorization and resends the request with payment proof.

Payment-Signature: 0x...

4

Access

Get Response

Facilitator verifies & settles the payment on-chain. Agent receives the API response.

200 OK + data

1

Request

Agent Calls API

AI agent sends a standard HTTP request to a paid API endpoint.

GET /api/translate

2

402

Payment Required

Server responds with HTTP 402 and payment requirements (amount, token, address).

402 Payment Required

3

Pay

Sign & Pay

Agent signs a USDC payment authorization and resends the request with payment proof.

Payment-Signature: 0x...

4

Access

Get Response

Facilitator verifies & settles the payment on-chain. Agent receives the API response.

200 OK + data

Integration

Agentic Wallets by Coinbase

Powered by Coinbase Developer Platform (CDP), agentic wallets give AI agents their own crypto wallets with programmable spending controls.

AI Agent

Autonomous Task

Agentic Wallet

Coinbase CDP

x402 Payment

Sign & Send

API Access

Get Response

AI Agent

Autonomous Task

Agentic Wallet

Coinbase CDP

x402 Payment

Sign & Send

API Access

Get Response

Autonomous API Discovery

Agent discovers new APIs, evaluates pricing from 402 responses, and pays on-demand — no pre-registration needed.

Budget-Controlled Spending

Set spending limits per agent, per task, or per time period. Wallet enforces constraints on-chain.

Multi-Agent Collaboration

Multiple agents share a single wallet or operate independent wallets. Each transaction is auditable on-chain.

Why x402Relay

Start Free with Coinbase. Get Chosen by AI Agents with x402Relay.

Coinbase provides the payment rails. x402Relay builds the marketplace where AI agents actually find and choose your API.

Feature	Coinbase CDP	x402Relay
Agent Marketplace	—	✓
JPYC (JPY Stablecoin)	—	✓
Gateway (Zero Code Change)	—	✓
Dashboard & Analytics	—	✓
AI-Native Design (llms.txt)	—	✓
Basic Payment (verify/settle)	✓	✓
USDC on Base	✓	✓
Free Tier	✓	✓

Being discoverable by AI agents is the new competitive advantage. Join the waitlist to list your API on the Agent Marketplace.

Components

Everything You Need to Monetize APIs

x402Relay provides a complete stack — from the Agent Marketplace where AI agents discover your services, to the x402 Crawler that verifies every API.

Payment Gateway

Reverse proxy that intercepts 402 responses, handles payment flows, and manages on-chain settlements transparently.

Facilitator

Verify and settle x402 payments on-chain. Supports EIP-3009 (USDC native) and Permit2 (ERC-20 universal).

Agent Marketplace

The verified API catalog for AI agents. x402 Crawler tests and validates every service, so agents can discover, compare, and connect with confidence.

TypeScript SDK

Client and server SDKs for TypeScript. Add x402 payments to your API in 3 lines of code, or consume paid APIs seamlessly.

Dashboard

Real-time revenue analytics, transaction monitoring, and usage insights. See exactly how AI agents interact with your APIs.

Use Cases

Built for the Agentic Economy

From micro-payments to premium data feeds — x402 enables new business models for the AI era.

Translation

AI Translation API

Charge $0.001 per translation request. AI agents pay per-call with USDC or JPYC — no subscription needed.

POST /translate → 402 → Pay $0.001 USDC or 0.15 JPYC → Get translation

Data

Premium Data Feeds

Sell real-time market data, weather feeds, or analytics. Micro-payments make premium data accessible to any agent.

GET /market/BTC → 402 → Pay $0.01 USDC → Get live price

MCP

MCP Server Billing

Monetize Model Context Protocol servers. Charge per tool call so LLMs pay for external capabilities on demand.

MCP tool call → 402 → Pay $0.005 USDC → Execute tool

Developer Experience

3 Lines to Monetize Any API

Drop-in middleware for servers. Transparent payment handling for clients. Works with any HTTP framework.

Server — Gateway Config

gateway.yaml

# gateway.yaml — Monetize your API in 3 lines
upstream: "http://localhost:3000"

routes:
  - path: "/api/translate"
    price:
      amount: "1000"        # $0.001 USDC
      network: "eip155:8453" # Base L2
      asset: "USDC"

# Start the gateway
# $ x402-gateway start --config gateway.yaml

Client — AI Agent

client.ts

// client.ts — Pay for APIs automatically
import { x402Client } from "@x402relay/sdk"

const client = x402Client({
  walletProvider: agentWallet,  // Coinbase Agentic Wallet
})

// Works just like fetch() — handles 402 automatically
const response = await client.fetch(
  "https://api.example.com/translate",
  {
    method: "POST",
    body: JSON.stringify({ text: "Hello" }),
  }
)
const data = await response.json()
// Payment handled transparently!

Roadmap

Building the Future of Machine Payments

From testnet prototype to production-ready infrastructure for the agentic economy.

Phase 0In Progress

Foundation

Facilitator server (verify & settle)
EIP-3009 (USDC) on Base Sepolia
Basic Gateway reverse proxy
TypeScript SDK (x402Client)

Phase 1Planned

Production

Base Mainnet deployment
Agent Marketplace — verified API catalog
x402 Crawler — automated API testing & validation
Dashboard & analytics
Rate limiting & abuse prevention

Phase 2Future

Scale

JPYC (JPY stablecoin) support
Multi-chain support (Ethereum, Solana)
Subscription & streaming payments
Advanced agent wallet integrations
Decentralized facilitator network

FAQ

Frequently Asked Questions

Get Early Access

Ready to Build the Agentic Economy?

Join the waitlist to get early access to x402Relay. Be the first to monetize your APIs for AI agents.

GitHub x402 Spec Coinbase CDP Docs