x402

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x402

x402 is a payment protocol that unlocks HTTP 402 Payment Required, turning it into a working payment system for AI agents and applications. The protocol enables programmatic, autonomous payments without requiring accounts, credit cards, or manual human intervention. Built on EIP-3009 (transferWithAuthorization), x402 allows AI agents to discover services, understand pricing, sign payment authorizations, and pay for API access—all automatically through HTTP requests and responses.

The protocol is designed for machine-to-machine payments, making it ideal for AI agents that need to pay for API access, data services, or computational resources. With x402, payments are as simple as an HTTP request: when an agent requests a paid resource, the server responds with HTTP 402 and payment instructions. The agent then signs a payment payload, retries the request with an X-PAYMENT header, and receives the resource—all without human intervention.

General
Release date	2024
Author	Coinbase
Documentation	x402 Documentation
Repository	GitHub
Type	Payment Protocol

Start building with x402

x402 makes payments HTTP-native, enabling AI agents to autonomously discover and pay for services. The protocol supports gasless payments through facilitators, works with any EIP-3009 token (USDC by default), and provides SDKs for popular frameworks like Express and Axios. Whether you're building a paid API service or an AI agent that needs to purchase resources, x402 simplifies the payment flow into standard HTTP requests and responses. Check out the community-built x402 use cases and applications to see what others are building.

x402 Tutorials

x402 Resources

Essential resources to help you get started with x402:

x402 Documentation - Complete documentation and guides
x402 GitHub Repository - Open-source x402 protocol implementation
CDP Facilitator Docs - Coinbase Developer Platform facilitator documentation
EIP-3009 Specification - The Ethereum standard that x402 is built on

x402 Libraries and SDKs

Official and community libraries for integrating x402 into your applications:

@x402/core - Core x402 protocol types and utilities
@x402/express - Express middleware for x402 payments
@x402/axios - Axios interceptor for automatic payment handling
@x402/evm - EVM-specific payment schemes (EIP-3009 support)

x402 Integrations

Connect x402 with your favorite frameworks and tools:

Express.js: Use @x402/express middleware to protect API endpoints with payment requirements
Axios: Use @x402/axios to automatically handle 402 responses and payment flows in client applications
React: Build React applications that automatically pay for API access using x402
Node.js: Integrate x402 into any Node.js application for server-side payment processing

x402 Features

Key features that make x402 powerful for AI-to-AI payments:

HTTP-Native: Payments work through standard HTTP requests and responses
Gasless Payments: Facilitators sponsor gas fees, making payments seamless
No Accounts Required: Payments work with crypto wallets, no account creation needed
Autonomous: AI agents can discover, understand pricing, and pay without human intervention
Universal Compatibility: Works with any EIP-3009 token (USDC by default)
Framework Support: SDKs available for Express, Axios, and more

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Coinbase x402 AI technology Hackathon projects

Discover innovative solutions crafted with Coinbase x402 AI technology, developed by our community members during our engaging hackathons.

RoboBazaar

RoboBazaar is a decentralized skill marketplace that enables robots to autonomously hire and pay human workers using the X402 payment protocol on the Base network. In real-world logistics and warehouse environments, robots handle approximately 80% of tasks autonomously. However, the remaining 20% — involving irregular, fragile, or oddly-shaped items — still require human dexterity and judgment. When a robot encounters such a task, it dynamically calculates a bounty based on item weight, danger level, and urgency. It then broadcasts a help request with a USDC reward. Nearby human operators receive the request on a dashboard, accept the task, and physically assist the robot. Upon task completion, the robot verifies the result using its onboard camera and triggers an automatic X402 micropayment to the human's wallet. Our system consists of four core components: (1) An AI FinanceAgent powered by LLMs that decides when to spend money on human help, (2) A Webots simulation demonstrating multi-robot coordination in a warehouse, (3) A bridge layer connecting simulation signals to the agent brain, and (4) A frontend dashboard for human operators to monitor bounties and accept tasks. Every human intervention generates labeled training data, creating a powerful data flywheel: more help → better data → smarter robots → fewer interventions needed. RoboBazaar doesn't build algorithms — it builds the commercial infrastructure to monetize them. We take a 5% platform fee on every transaction while enabling algorithm developers to earn passive income when their skills are purchased by robots in the field.

MEV-shield circle payment

Problem: Monthly subscriptions ($50-$500) for MEV analytics waste capacity, block AI agents from autonomous access, and traditional payment fees (~$0.30+2.9%) make pay-per-query impossible. Solution: x402 micropayments enable humans and AI agents to pay only for what they use. How it works: x402 Protocol: Returns HTTP 402 with exact price ($0.01-$0.05/query)—machine-readable pricing replaces opaque tiers Circle Wallets: Onchain treasury with guardrails ($1/tx, $10/day)—AI agents spend autonomously without human approval Arc Network: Near-zero fees (~$0.003) settle $0.05 payments in ~2 seconds using native USDC gas.

AutoWealth Agent

AutoWealth is an autonomous AI financial agent designed to modernize how automated services transact. Instead of giving AI agents unrestricted access to funds or requiring manual approval for every action, AutoWealth operates on a rigorous policy-driven engine. Users interact with a "Financial Advisor" AI to define budget guardrails (e.g., "Spend max $5/day on inference," "Only approve Education category"). Once these policies are active, the "Buyer" agent can autonomously discover services and execute real-time micropayments using the x402 protocol, ensuring the user maintains full control without constant manual intervention. We leverage the Arc blockchain for a transparent, immutable audit trail of every transaction.

HumanGrid AI- The Error-Handling Layer for Agents

We are entering the era of Autonomous AI Agents, yet even the most advanced models (like Gemini or GPT-4) suffer from the "Last Mile Reliability Problem." When an agent encounters ambiguous data, sarcasm, or high-stakes verification tasks, it often hallucinates or crashes. There is currently no standard API for an AI to programmatically ask a human for help. HumanGrid AI is the error-handling layer for the autonomous economy. We have built a decentralized marketplace where AI agents can offload confusing tasks to a global grid of human workers in milliseconds. How It Works: The Trigger: An AI Agent (powered by Google Gemini) detects low confidence in a task. The Handoff: The agent calls the HumanGrid API, posting the task with a bounty. The Work: A human verifies the data via our real-time dashboard. The Agentic Payment: Using Circle Developer-Controlled Wallets, the agent autonomously pays the worker in USDC on the Arc Network. Why This Matters: By leveraging Arc’s sub-second finality and Circle’s programmable wallets, we transform AI verification from a slow, manual process into a high-speed, agentic transaction. This creates a symbiotic economy where agents act as employers and humans provide the intuition that code lacks. Tech Stack: AI: Google Gemini Flash 1.5 (Function Calling) Settlement: Arc Testnet (Native USDC Gas) Payments: Circle Programmable Wallets (Agent Treasury) Backend: Rust (Axum) for high-performance verification Frontend: Next.js with Real-time Supabase integration

SocratIQ

# SocratIQ: Autonomous Knowledge Refinery — Summary SocratIQ is a decentralized marketplace that changes how AI improves itself. Instead of humans querying AI, AI agents autonomously detect their own knowledge gaps and purchase high-quality human reasoning using USDC on the Arc blockchain. This creates a sustainable loop where human expertise is monetized, AI models avoid reasoning decay, and knowledge exchange is transparent, trustless, and efficient. ## The Problem Modern AI systems face model decay from synthetic data, struggle with cultural nuance, ethics, advanced reasoning, and real-time expertise, and rely on inefficient alignment methods like RLHF. Meanwhile, human experts lack scalable ways to monetize deep thinking, and authentic human insight is increasingly buried under AI-generated content. ## The Solution SocratIQ acts as an Autonomous Knowledge Refinery, aligning AI demand with human expertise via smart contracts and decentralized verification. ### Key Roles * Procurers: AI agents with USDC treasuries that post bounties * Refiners: Human experts providing high-order reasoning * Arbiters: Decentralized AI juries validating quality * Settlement: Instant, predictable USDC payments on Arc ## How It Works AI agents monitor confidence levels and post bounties when uncertainty arises. Tasks are matched through a tiered marketplace (from quick fact checks to expert consultation). Submissions are verified by a multi-model AI jury, and payments are streamed via Circle’s x402 protocol in milestones, reducing risk and enabling feedback. ## Use Cases Healthcare diagnostics, legal research, scientific discovery, culturally sensitive customer support, etc. ## Advantages & Impact SocratIQ offers first-mover advantage, decentralized quality assurance, instant settlement, resale royalties, etc. ## Future Multi-modal bounties, federated learning, DAO governance, cross-chain expansion, and domain-specific marketplaces.

ClickTreats- The Agentic Data Exchange

ClickTreats is a next-generation decentralized marketplace for the agentic data economy, where individuals reclaim ownership of their digital footprint and monetize it through autonomous AI agents and instant blockchain settlement. Today, browsing data powers a massive multi-hundred-billion-dollar industry, yet individual users receive none of the value they create. Advertisers, data brokers, and AI companies profit from behavioral exhaust while users remain uncompensated. ClickTreats was built to reverse this model by transforming passive browsing into an active, user-owned asset class. At its core, ClickTreats allows verified humans to package, license, and rent their browsing data directly to buyers, with payments settled instantly in USDC and enforced by smart contracts. How It Works For sellers, a Chrome extension collects browsing events with explicit user consent. A local AI “Packaging Engine” organizes raw activity into structured Data Packages (shopping intent, SaaS research, travel planning, crypto behavior, and more). Users can list these packages on the marketplace or license them for fixed time windows, retaining full ownership of their data. For buyers, ClickTreats introduces autonomous procurement. Instead of manually browsing listings, buyers submit objectives such as “Acquire high-intent luxury footwear shoppers.” A Gemini-powered AI agent scans the marketplace, evaluates seller reputation, predicts ROI, and autonomously executes purchases using x402 micropayments. A real-time Thinking Log displays the agent’s internal reasoning, making every transaction transparent and auditable. All users are verified through World ID to guarantee that every data point comes from a real human. This human-verification layer increases data quality and prevents bot-generated market pollution.