Preamble out of the way, the Keyword Policy page says to tag sex, in no uncertain terms, and in bold letters. As this one says "policy" in the name, I assume it is the authoritative source.
The Keywords page says to tag gender, again with the certainty of bold lettering, but then just below that defines men and boys as having "male genitalia," and women and girls as having "female genitalia."
Taken as a whole, the guidance is contradictory, but skews toward tagging based exclusively on genitalia. I've asked staff about this, as I assume that if re-examined they would not choose to intentionally exclude trans characters and, often by extension, their creators. Not much time at all has passed since I asked, and while I do expect to receive one, I have not yet.
Frankly, if the guidance is intended to disregard trans identity, I just won't comply with it. After all,
"
The account owner has the final say in what keywords apply to their submission.
Still, clearer (and preferably affirming, of course) guidance would be desirable.
UPDATE: A member of staff has responded to say that in place of "male," for instance, "ftm" could be used in isolation for a piece featuring a transgender male, and that "ftm/male" would be better in this instance than "male/male" for a piece featuring a transgender and a cisgender male.
This is not exactly my preferred conclusion, and the rules should be rewritten to support it, but it does seem a very reasonable compromise between making tags useful to find certain visual content and allowing them to accurately represent a character's gender.
