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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 date2024
AuthorCoinbase
Documentationx402 Documentation
RepositoryGitHub
TypePayment 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 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.

ReproClaw: Pay Per Claim AI Audits

ReproClaw: Pay Per Claim AI Audits

ReproClaw is a pay per claim reproducibility audit agent for AI research. A user submits an arXiv paper and GitHub repository, and ReproClaw extracts scientific claims, maps each claim to code evidence, checks for mismatches, and generates a verifiable audit report. For example, if a paper claims a model was trained for 200 epochs or achieved 81.5 percent accuracy, ReproClaw searches the implementation, config files, README, and evaluation scripts to verify whether the code supports that claim. The system produces a reproducibility score, verified claims, flagged claims, and reviewer ready explanations. For the Agentic Economy on Arc hackathon, we extend ReproClaw with usage based payments. Instead of charging for a full expensive review, users can pay per claim, per repo search, per citation check, or per dynamic execution. Circle Nanopayments and USDC make this possible by enabling small, high frequency, gas free payments for individual agent actions. ReproClaw turns scientific verification into an on demand agentic service: transparent, modular, and economically aligned with actual usage.

Arc Power

Arc Power

nano-agent treats cost as a live reasoning input. At every step, the agent decides: proceed, downgrade to a cheaper model, or skip — governed by a real USDC budget settled on Arc via Circle Gateway. Gemini 2.0 Flash handles fast inference, function calling, and Google Search grounding. Gemini 2.5 Pro verifies factual claims. Each tool call triggers HTTP 402 — the agent signs an EIP-3009 USDC authorization and retries with payment proof. Circle Gateway settles micropayments on Arc in under a second at sub-cent cost. A live dashboard shows spend, earned, step count, and model-tier decisions in real time. Benchmark: 416 steps · $0.240 spent · $0.276 earned · +15% margin · $0.0006/action average. A screen recording shows a $0.25 live run — budget bar draining, model tier switching, decision log printing go · downgrade · skip. Economy view breaks down cost: 77% data, 17% LLM, 4% verification. Two agent wallets earn independent revenue. TAM is $200B+ AI infrastructure. SAM is $15B agentic API economy — every autonomous agent calling external services is a potential payer. Revenue comes from per-step settlement margin, SDK licensing, and premium x402 tool endpoints with built-in payment rails. LangChain, AutoGen, and CrewAI treat cost as post-hoc billing. nano-agent makes it a real-time constraint on behavior. The Arc economics are the moat: the same 417 actions cost roughly $834 in Ethereum gas — 3,475 times more expensive — making per-step micropayments impossible anywhere else. On Arc mainnet, multi-agent economies — agents hiring agents, earning revenue — become self-sustaining. Every x402-compatible API becomes a paid tool layer. nano-agent is the budget runtime that keeps those economies solvent.

ARC-Agents Marketplace

ARC-Agents Marketplace

Agents Market is a demo marketplace for autonomous agents and their tools on Circle Arc (testnet). Sellers onboard listings with per-tool USDC pricing; the app supports discovery, catalog views, and payment-gated invocation of seller-configured HTTP providers. The stack implements two payment rails so different buyers can participate without one-size-fits-all custody. External buyers integrate Circle Gateway Nanopayments over standard HTTP 402 flows (e.g. via circlekit on arcTestnet), which fits agent-to-agent and pay-per-call use cases. Registered marketplace buyers use USDC on ARC-TESTNET through Circle developer-controlled wallets, including automatic wallet provisioning when no address is supplied, on-chain USDC transfers for settlement, and optional ERC-8004-style lifecycle hooks for agent registration and reputation on Arc. The FastAPI backend combines marketplace CRUD, SQL persistence for usage and payment events, provider proxying with safety checks on outbound hosts, and APIs that expose a clear description of which rail was used. The React frontend supports browsing agents, registering listings, editing tool prices, and reviewing activity with Arcscan links so judges and developers can verify flows on chain. Together, the project shows how USDC-first infrastructure, nanopayments, and hosted wallets can support a scalable pattern for monetized agent commerce.

Arc Data Piper

Arc Data Piper

ArcDataPiper is a revolutionary "Pay-as-you-Heal" infrastructure layer designed to solve the $3.1 trillion problem of data quality and pipeline downtime. Traditional data monitoring relies on expensive, static subscriptions that alert humans but don't fix problems. ArcDataPiper flips the script by turning infrastructure health into a granular economic commodity. Built on the Arc Network, the system utilizes Circle Nanopayments to implement a "Pay-as-you-Live" monitoring model: you only pay for monitoring as long as your stream is healthy. When Schema Drift is detected in a Kafka/Redpanda stream, the LangGraph-driven orchestrator pauses billing and hires a "Recovery Team" of Gemini 1.5 Pro agents. A Fixer Agent analyzes the Dead Letter Queue to generate a real-time JavaScript transformation patch, which is then audited by a Verifier Agent. To ensure absolute reliability, we utilize a Pay-on-Outcome bounty system: the Fixer is only paid their USDC bounty if the fix is validated and the stream resumes. By leveraging the sub-second finality of Arc and the reasoning power of Google DeepMind's Gemini, ArcDataPiper reduces Mean Time to Recovery (MTTR) from hours to seconds, creating the first truly anti-fragile, self-sustaining data economy.

QuickSilver

QuickSilver

QuickSilver is the world’s first Autonomous Work Exchange, a self-optimizing marketplace designed to dismantle the inefficiency of traditional SaaS subscriptions. While current software models force users into expensive monthly fees for tools they use sporadically, QuickSilver introduces a granular, pay-as-you-go ecosystem settled via sub-cent USDC nanopayments. Built on the Arc L1 blockchain using Circle x402, the platform collapses transaction costs to near-zero, allowing for $0.005 API calls that remain profitable. The architecture consists of an API layer for sovereign agent discovery, a marketplace governed by the mathematical EigenTrust reputation system to prevent fake reviews, and a visual Cloud Canvas where "Agentic Blocks" hire specialized AI services at the millisecond of execution. To solve the "cold-start" trust problem, an Auditor Bootstrap Node verifies new sellers, granting them immediate visibility through a genesis seed node. QuickSilver monetizes through a 2–5% curation fee on agent calls, a 10% seller commission, and a tiered cloud subscription model. By combining real-time programmatic hiring with high-fidelity settlement, it transforms static automation into a dynamic, cognitive economy where agents and humans collaborate seamlessly without the friction of gas fees or rigid subscriptions.

CareRoute

CareRoute

CareRoute is a clinical workflow assistant built for the Agentic Economy on Arc. Instead of treating healthcare intake like a flat-fee SaaS workflow, CareRoute prices each reasoning step independently and settles those steps onchain in sub-cent USDC amounts. A user connects a wallet on Arc Testnet, funds a small case budget, and submits symptom intake. An orchestrator agent summarizes the case and routes it only to the specialist agents that are actually needed. Cardiology, neurology, respiratory, and general review agents return structured findings, while a verifier agent aggregates the outputs into a final workflow-ready report with risk flags and urgency. CareRoute is intentionally framed as a clinical intake and routing assistant, not diagnosis software. That makes the product safer and clearer. The demo shows how a real user-funded case budget is consumed step by step by specialist agents instead of forcing a subscription or flat platform fee for a short-lived workflow. Users pay only for the compute and specialist review actually used on a case. This fits the hackathon especially well because the workflow is only viable when payments can happen at very small denominations and high frequency. A case may involve intake summarization, one or more specialist reviews, and a verifier pass, each priced below one cent. Arc makes that model credible with fast, stablecoin-native settlement. In the live product, users can see the funding transaction, downstream specialist payouts, and the final structured output in one dashboard. CareRoute uses Next.js, wagmi, RainbowKit, viem, Arc Testnet, USDC, and AI/ML API.