if anything, the op had it correct with fedi:// or ap://

the requests and responses standardized as with any protocol regardless of underlying server.

objects in the fediverse are urls. thats just how it works.

apps (clients) accessing that content are outside the scope of the protocol.. its their own implementation problem with how they render stuff (those object urls).

for example; mbin can already consume/ingest a given fediverse thread, post or comment if it has never seen it before (given the url) and render it correctly.