There is some documentation for the members of the fsi
object available in the F# docs. This is a bit tricky to find, because fsi
is a value of type InteractiveSession
and so you need to look for the type, rather than just for fsi
value.
It is also worth noting that, in addition to using reflection to see the members, you can also see all members if you type fsi
followed by .
(at least in Visual Studio) and the names of the members are fairly descriptive (though figuring out the details is a bit fiddly sometimes).
I'm not sure if the documentation is complete, but the docs are hosted on GitHub and anyone can contribute to improve them and add examples.