Is there an object model doc for Inform 7?

You might try this thread for several different approaches to documentation. I don’t know if anyone’s written up a formal object model, though.

As for your example:

[code]the list of things in the location of the player [if you’re concerned with direct containment only]

the list of things enclosed by the location of the player [if you want to count things inside of things as well][/code]