<sorttitle> is the field we use, this is supported on both movies and TV shows.
<uniqueid> is supported for episodes, yes. It is encouraged to use this as you’ll get more stable guids (for watch history, rating, etc.)
<mpaa> is currently only supported at the show level. I can file an issue to add this for episodes too.
<ratings> is supported for episodes.
Some things may have been left out in the docs for brevity, I’ll ask somebody to add these missing things.
