On the note of what a future API might allow, i'd presume it'd allow everything that the game currently displays. The game does have an innate parser, the devs have shown it in a screenshot of the dev environment (which they were using to showcase the Garuda fight before release) and it's used in PVP, however, they have purposefully left it out of the game's PVE environment, presumably because they don't want it there.
So I presume that enmity values, healths, statuses, form of widgets etc. is good to believe will be avaiable, a parser-like too, however... I doubt