What about having a tag class and subclass.

So you can have something like

notsafe.gore and notsafe.nudity and notsafe.violence

Or info.contributor or info.some_other_info

E.g. the top level “classes” would be somewhat standard and have a “meaning” while the subclass would be for more granular details.

So clients/servers can just look at the first token for simple filtering (no nsfw) or more granular (I’m ok with nsfw of this but not that)