HTTP 402 + USDC: Pay-per-use AI APIs for Autonomous Agents

The Problem with API Keys for AI Agents AI agents need to call external APIs autonomously. But traditional API key auth has a fundamental mismatch: Who manages the keys? The agent can't sign up for accounts How does billing work? Subscription tiers don't fit pay-per-task usage What about multi-agent systems? Keys get shared, leaked, revoked There's a better way: let agents pay directly, per request, with crypto. x402: HTTP 402 as a Payment Protocol The HTTP 402 status code has been "reserved for future use" since 1991. x402 finally uses it. The flow: Agent → POST /document-intel Server → 402 Payment Required { amount: "0.05", currency: "USDC", network: "eip155:8453" } Agent → EIP-3009 signature (gasless transfer authorization) Server → Facilitator validates → 200 OK + result No API keys. No subscriptions. No gas fees. The payment IS the authentication. ntriq AgentShop: 6 Endpoints, $0.01–$0.05 We built a document intelligence server on this protocol, running 100% local inference on a M