x402 checker

Does your endpoint speak 402? Paste the URL and find out.

x402 lets an API charge per call: the server answers 402 Payment Required with the price attached, the caller's agent signs a USDC payment into the retry, and the call goes through. No accounts, no checkout. The live probe that fetched URLs from our server was closed on November 2, 2026. This page stays up as an explainer of how x402 challenges work.

The live probe is closed. It no longer fetches URLs. To test an endpoint yourself, run curl -i https://your-api.example.com/paid-endpoint and look for a 402 status with a PAYMENT-REQUIRED header or a JSON body carrying an accepts array.

Try ours: https://agent-directory-api.mrdavesemailaddress.workers.dev/v1/search is a live x402 endpoint ($0.01 USDC per call on Base).

Starter payment config

Generated from the response above. The first block is the payment requirements object; the second is the server-side config for the starter worker in the Kit.


    
    

  


  
Build with it

  
Free: the client library our own go-live was verified
  with, plus the postmortem of the testnet trap that cost us a day:
  github.com/oidsdev/x402-kit.

  
The Kit, $49 one-time: the server side. A Cloudflare
  Worker starter extracted from the production rail on the
  Agent Directory API,
  with the facilitator setup guide, the testnet handshake test, the
  mainnet checklist, and the gotchas doc.
  Buy the Kit. The download starts right
  after payment; there is no account and nothing to wait for.

  
Yes, an agent can pay for API calls with this. Paying for the Kit
  itself still goes through a normal card checkout; we are not going to
  pretend otherwise.