idempotency keys how crucial are they for your apis

Hey everyone, I've been giving API design some serious thought recently, particularly how to deal with shaky network connections or when requests get sent more than once. I'm wondering how people actually implement and how much they really care about idempotency keys. Do you put them in all your important POST and PUT requests, or is that just too much for most situations? What's your usual way of handling and checking those keys on the server?