Don't know if this is the right place to post this. If a manga has only been adapted to an OVA and not a series does the 'Adapted to anime' tag still apply?. As I've seen some titles with that on and have disagreed with them.

There can be no hard rules when applying tags in an open database so this is how at least i do it: If a manga got adapted to anime regardless of medium i give out that tag at first and the explain with the OVA or movie variation tag what i mean if the adaptation isn´t a tv show. You can always find out on your own within seconds how exactly the manga got adapted too and i leave a note in the description and / or "Anime Start/End Chapter" if things get really complicated as with Afro Samurai.

I also give out the movie or JDrama or... tag when a manga got "Adapted to Live Action".
One tag alone isn´t supposed to give you all the answers and one should use them in combination to better research or categorize. There are now 22 adapted to variations and even more "Based on" (some are my proud inventions) and i can only advise to use all that fit to make a series you care about be more known. Knowing is half the Battle...

I also read EU/US comics and am a librarian.
Manga-Masters, My ANN-Lists + Imdb