What x402 means
x402 is a payment protocol built around the HTTP 402 status code. The server returns payment terms; the client pays and retries with proof of payment.
Instead of forcing every agent through signup, card forms, and API-key email, a priced route can answer with machine-readable price, network, asset, and pay-to details.
Passing an x402 check means the response shape looks ready. It does not prove the service is useful, safe, or correctly priced for your buyers.
Test the exact URL agents will call. A homepage that returns 200 or 403 is not the same as a paid route that returns 402.
Why this matters for builders
You need it when AI agents should buy an API call, file, or tool result without creating an account first.
Mistake builders make often
Marketing “agent payments” while the live route redirects or blocks with auth before any 402 payment terms appear.
What to do now
Paste your paid HTTPS endpoint into the free x402 endpoint checker and fix failed required checks first.