The AI Agent Economy Needs Payment Rails — Here's What I Built

500K+ AI agent wallets exist on x402. Stripe launched machine payment protocols. Google announced AP2. The infrastructure for autonomous AI commerce is being built right now. I wanted to test the thesis: can you build a service that AI agents pay for, with zero human intermediaries? The Experiment I built a trading signal API. Agents call an endpoint, pay $0.005 in USDC on Base L2 via x402, and get back momentum signals (RSI, ADX, MACD, volume, composite score). No signup. No API keys. No subscriptions. No humans in the loop. What I Learned x402 makes this trivial.