Microsofts referencesource. Meaning published source for closed source libraries. No amount of documentation beats being able to see for yourself not just what the software will do not only the documented/supported scenarios but also in undocumented ones.
But just because the Microsoft API documentation is always very meaningless. This could be from their docs:
class SomethingProvider: "Provides functionality for communication with something"
property string SomethingUrl: "Gets/sets the URL for the something endpoint"
function Initialize(string[] roles): "Initializes Something-Provider with the given roles"
