wish: document each part of the return value

[markstos]

An example return value is structure, but the elements are not documented. What exactly goes in a "unit" vs a "number"? The "parts" field just shows an empty array as example. An actual example value would be helpful.

[DamonOehlman]

Sure thing - will document this when I'm documenting #4. It might be a couple of days until I can get to it as I'm a bit snowed under with some other work at the moment...