One other point that hasn't really been covered is reproduction. It's not something you usually worry about (as a goal) for a one-night stand, but in a potential long term relationship the partner should probably be aware fairly early on that if kids are going to be in the picture, adoption or surrogacy/sperm donors will probably be involved.

I think if you've got anything physical that might be a deal breaker for the other person, it should probably come out well before sex. When it comes to equipment, it's best if you don't surprise your partner. Cis guys who are extremely short or extremely long in a certain area are in this boat, as are people with nerve damage, medical conditions, ill-considered tattoos, birth defects, extremely strong fetishes, or even things like skin discoloration or oddly shaped birthmarks. The majority of trans people do end up in this category, but having to disclose some physical complications that may result in a potential partner withdrawing consent isn't limited to trans people.