How to Verify Paid APIs Before Your AI Agent Spends Money

AI agents are starting to pay for API calls autonomously. Protocols like L402 (Lightning Network), x402 (Coinbase/Base), and MPP (Stripe/Tempo) let APIs charge per request using HTTP 402 — the "Payment Required" status code that's been reserved since the 1990s. But here's the problem: how does your agent know the endpoint is actually worth paying for? An endpoint might be listed in a directory. It might have been healthy yesterday. But right now, at the moment your agent is about to commit funds — is it live? Is the SSL valid? Is the payment handshake properly configured? Or is your agent about to send money into a broken endpoint? The pre-flight check pattern Before any paid API call, run a pre-flight check. Think of it like a pilot checking instruments before takeoff — you don't skip it just because the plane flew fine yesterday. We built paid-api-preflight as a Strale capability that does exactly this. Pass it any URL, and it returns: Whether the endpoint is reachable Response time