402 Probe

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Before paying, ask: is this URL really an x402 endpoint right now, and under what exact terms? Probe returns the scheme, network, asset, amount, payTo and timeout of the payment challenge — plus a validity check of the challenge itself. Optionally reads /.well-known/x402 on the same origin.

How to use

  1. Paste any API URL you are about to pay.
  2. Pick a method (GET defaults; 404/405 auto-retries as POST).
  3. Run — see whether it returns 402 and the exact payment terms.
  4. Use the challenge-validity flag to decide whether to proceed to payment.
  5. Agents call the paid POST /api/402-probe endpoint ($0.002).

Where it applies

  • Verifying an endpoint is still x402 before sending USDC.
  • Reading payTo / amount / network from the live challenge.
  • Checking a listed service from a directory before first payment.
  • Detecting endpoints that silently stopped requiring payment.