The host an operation's own document declares as its server, checked by DNS and a TLS handshake on 2026-09-10 - no HTTP request, no path touched. This is the failure that looks like nothing until the call.
890 records across 476 subjects, observed 2026-09-10. Every one carries a check you can run in a single request.
All subjects · the whole registry, machine-readable
Asking about something not listed here, before you use it — one request, no key: GET https://apidefects.com/check?tool=<identity>. never_examined is an answer too, and it is not a clean bill of health.
This is not a list of good APIs or bad ones. It is a list of observations, each dated and each disprovable in one request. Absence from it means an operation was not examined, not that it is fine.