It's really use case specific in my case - things like having a selected key should be straightforward enough, but some of my components weren't written with that in mind. It's little things like that that make me say it's a good exercise - many of the difficulties are my own fault, which means it's easy to learn from my mistakes.

Music theory in general is a somewhat difficult abstraction due to the multiple ways to interpret different things in different contexts. The same chord progression might be thought of as being in several different keys based on other contextual information for example.