Use health checks and synthetic probes to tell carrier failures apart from your own regressions.
A good health check does more than confirm the process is alive. For carrier integrations, it should separate local health, dependency reachability, credential validity, and critical-path readiness. Lightweight synthetic probes against the safest carrier endpoints can reveal auth or routing failures before customers find them.
Do not overload one endpoint with every possible dependency test. Split liveness, readiness, and deeper diagnostic probes so deploy systems and humans get the right signal.