At the behest of Snow Wolf this is getting its own dedicated thread.
TL;DR:
Tentacles designed to be penetrated (as opposed to the more common ones that penetrate you) are a bit of a mess, tag-wise

Picking up from where we left off in the "do we have a tag for this" thread:

Levant said:
Tagged as maw:
post #1611374 post #807032
(last one is also tagged as mouth, though likely because of what behind him instead of the one in front)

Tagged as mouth:
post #60700 post #500407

Tagged as pussy:
post #1518668 post #499829

Of those six, only half of them are tagged with fellatio, since the right kind penetration isn't quite there yet, though they're still tentacles that you penetrate rather than the other way around. Furthermore...

Tagged as Maw:
post #1407603 post #79420

Tagged as Mouth:
post #97833 post #1232019

All four cases are technically correct. The first two have tentacles with petal-like bits that open up, however you wouldn't be able to penetrate either. While the last two do certainly have mouths, and by extension, holes, they're still clearly designed to give, not take (also applies to cases like post #821420 where the presence of tongues implies mouths, even though there's no real hole)

There's also yet more cases where the tentacle is just a bit too generic or abstract for the categories and ends up with fellatio without being labeled as maw, mouth, or pussy:

post #1405556 post #909983

I would suggest implementing something like a penetrable_tentacle tag, or re-purposing tentacle_pussy to be any tentacle designed to be penetrated

Tail pussy (post #965937 post #647044) May or may not be grouped in with this as well. There's arguments to be made for or against