I Built a Pay-Per-Call Trading Signal API for AI Agents

If you're building AI agents that trade, they need market signals. But most data APIs require human signup, API keys, and monthly subscriptions — none of which an autonomous agent can handle. I built a trading signal API where AI agents pay per call using the x402 protocol (USDC micropayments on Base L2). No signup, no API keys. Agent shows up, pays half a cent, gets data. How x402 Works x402 revives the HTTP 402 ("Payment Required") status code: Agent calls GET /signal/NVDA Server responds with