Use when you need to know whether a running system is in the state it should be — "is everything OK", before a change with blast radius, after a restart or power event, or when a health claim is about to bear load and someone is about to act on "it is fine". Do NOT fire when a specific thing is already known broken and you want the cause, when one metric you could read directly would answer it, or when the question is about a change you are making rather than the state you are in.
