Why check an API that's already listed?
Directory data can outlive the service it describes. An endpoint can disappear, stop returning a valid 402, change its payment destination or price, or lack enough information for an agent to construct the call.
402Signal keeps the listing and the runtime observation separate.
DISCOVERY
What sellers say is available
Catalogs, directories, and seller metadata. A listing can remain after the endpoint has changed.
402SIGNAL
Check it now
Valid x402? Payment terms? Invocation info? Fresh observation? The listing is not treated as the answer.
YOUR AGENT
Decide whether to spend
Own wallet. Sign the seller payment. Pay the seller. Call the API.
What a live check can establish
- Payment
- Did the endpoint return a valid, parseable x402 challenge?
- Payment terms
- What payTo, amount, asset and network did the endpoint return?
- Invocation
- Is there enough request information for an agent to construct the call?
- Freshness
- When did 402Signal make the observation?
Readiness
- Discovered
- Found in supported discovery infrastructure.
- Payable
- Valid HTTP 402, parseable payment requirements and usable payTo.
- Invocable
- Enough request/schema information exists for an autonomous agent to construct the call.
- Recently verified
- Passed a sufficiently fresh independent check.
Health and reliability only appear when there is enough history to support them.
402Signal stops before seller execution
402Signal recommends a route. The caller keeps its wallet, signs the seller payment and executes the seller request.
The $0.01 routing check pays 402Signal for the check itself. It is separate from whatever the selected seller charges.