Your rules applied
Send a price ceiling, allowed networks, a latency bound or a required input schema and the check returns the option that meets them, or a typed reason nothing did.
Request fieldsTry it
Run a real check on a listed endpoint. No wallet.
This is the unpaid readiness check, the same observation the paid check starts with. Pick a listed endpoint, or paste one from Explore, and see what the seller answers right now: whether it returns a valid challenge, the recipient it names, and when we looked.
Start with one buyers ask about
These four are catalog listings that answered recently. Each link prefills the field; the check runs only when you press the button.
agent402.tools web searchapi.kadec0.xyz search resultsx402.ottoai.services weathercrypto.apitoll.cloud token price
Check a listed endpoint
Listed endpoints only. An endpoint that is not in the catalog returns unlisted and nothing is contacted. The check is rate-limited per visitor.
What the paid check adds
Your rules, the selected terms, and a receipt.
A signed receipt
Ask for require_route_binding and the answer binds the exact request and the seller's whole challenge. Verify it offline before your wallet signs.
Hooks that refuse
The x402 and mppx hooks run the check inside your client and refuse to sign when the live challenge differs from the verified terms.
Add the hookAlerts when it changes
With an admission key, subscribe a webhook to the hosts you depend on and get a signed event when the price, recipient or liveness changes.
Change alertsWant to see the decision logic without an endpoint? The simulated example on the How page walks through matching, changed and expired offers. Evaluation credits for the paid check are available by email: ross@402signal.com. Pricing is on one page.