Fediverse memes

That's right. Flairs are not currently in the api (edit: tags as well, see edit at bottom). The focus on the initial api implementation was to work with existing lemmy apps/frontends, so flair wasn't prioritized (this is also why you don't see feeds/topics in the api except for a couple undocumented endpoints). The other docs page that Blaze linked is an ongoing rewrite of parts of the api/documentation as part of making the api self-documenting.

Now that the first pass at the api is done, it would make sense to come back and add them...however, there are changes to flair that need to happen in the near future, so I think it makes sense to hold off on adding them to the api until those changes happen. I would also want to add possible flair to community endpoints as well so that apps know what flair a new post could have.

Edit: I read too quickly and mistook flairs for tags. Everything I wrote above is accurate for flairs and is similar for tags. Tags are not present in the api at the moment, but could be added without breaking anything. It is simply a matter of prioritization. My effort at the moment is focused on the aforementioned self-documentation overhaul of the api which is what app creators said would be the most helpful to them.