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. About 10 lines of FastAPI middleware to gate any endpoint behind micropayments. The Coinbase facilitator handles verification and settlement.

The real bottleneck is discovery. How does an agent find your API? Right now, a human developer has to wire it in. True agent-to-agent discovery (where Agent A searches for "trading signals" and autonomously starts paying Agent B) is 12-18 months away.

Pricing for machines is different. Agents don't care about $9.99/month vs $12.99/month. They care about cost-per-call. Sub-cent micropayments change the economics entirely.

The Stack

• FastAPI with sync endpoints (yfinance blocks I/O)
• x402 Python SDK with ASGI middleware
• USDC on Base L2 (sub-cent gas costs)
• LRU cache, 5-min TTL
• Deployed on Fly.io (~$0/month)

What's Next

If this gets traction, the next step is a Bittensor subnet — decentralize the signal generation so miners compete to produce better signals, validators score against actual market performance.

Open source: https://github.com/pmestre-Forge/signal-api