I guess by which context (server/client)?
At least from what I remember, most things are pretty tolerant. Sometimes shown in the order it was discovered in (at least in a timeline).
You can always toy experimentally with this by just static files of the JSON-LD context, as long as the correct media type is served. Mastodon (out of all other implementations) just tends to be the most fickle, expecting WebFinger resolution and a few other prerequisites (in terms of "test labbing" with static JSON files), while most others just simply need a resolvable actor object.
