ToME: the Tales of Maj'Eyal

Basically what the title says, I feel like there should be a line in the description of every equipment restricted skill that goes along the line of "requires: [type of equipment]". For example, a skill useable only by characters equipped with a 2h weapon would read "requires: 2h weapon".

It would help clarity especially for people who want to try out certain adventurer builds but have no clue if things will mesh together, and I guess also for disarm, and probably other things I can't remember at the moment.

I agree with this.
For an example of problems (sans adventurer, even), just look at the Doombringer's 2h weapon tree.
I didn't even realize it was 2h specific for a while, since the only thing that says anything about that is the little blurb you get when mousing over the category name (which I rarely read, preferring to read the skills to see what they actually do).
I just happened to not have any desire to change what type of weapon I was wielding.

100% agreed.

Making prereqs more of a data-thing rather than a code-thing would mean more consistent presentation, and less frustration when trying niche builds.

Right now it's like code diving is required to know how things work, and that just sucks for non-coders.