I believe this question is now on topic.
The comments make the following objections:
I'm thinking it's the job of the person who asked you to "write a health check" to define what they mean by "health". Otherwise, it's just guesswork. – Jörg W Mittag 4 hours ago
I agree with @JörgWMittag comment, but I'd even take it a step further. You should get your requirements not only from the person who told you that you need to design a "health check", but also figure out who the people or systems are who use the data that is part of a health check and figure out what they need or how they need it. These are your requirements that will drive your design. – Thomas Owens♦ 2 hours ago
I believe that those perspectives are in fact valuable answers to this question.
Many programmers will have to add healthchecks to applications at some point. Understanding that there are multiple factors to consider, such as the above comments, is in my opinion the answer to this question.
For this reason I believe this question is a valuable and answerable question for both the asker as well as the broader programmer community.