I've been following this thread and thought I would pop in with what has worked for Whip and I so far.
I have less need/want to know about our sexual interactions with other partners than Whip does. He would tell me every little detail if I wanted. (He's definitely an exhibitionist and a voyeur.) And he would not mind at all if I tell him all my naughty details about sex with other people. (Although this not been tested much as I have found only one other person I wanted to be with and that fizzled.)
But I do not like knowing the details because I start playing the comparison game in my head. Well, if he did this-n-that with her, maybe he doesn't like it as much with me? She's younger than me, maybe he prefers that? She is wayyyy more submissive than me - maybe that is what he wants *really*. It is utterly irrational and unconnected with reality. What he does sexually with one partner does not impact us - except maybe as food for thought, for experimentation. If he wanted to only date younger (than me) women, he would. If he wanted a woman who is only submissive, then he would date someone like that. And he is not responsible for my little hamster wheel comparison game.
I find that not knowing details really helps to not play the comparison game. Eventually I may get to the point of details don't bother me but I am not there yet.
So what do we tell each other? We have agreed that 1) wherever possible, give a heads up if someone appears on the horizon as a possible partner. 1a) If a play partner or friend becomes a sexual partner, let the other know - this does not need to be done beforehand but is nice when possible. 2) We don't have a veto over partners but expect our opinions about potential partners to be considered. 3) If the relationship changes or evolves with someone else - for example a play partner may evolve in a FWB, or something more serious - please give a heads up to the other partner. And finally, 4) if fun was had. We do want to know if the other has had a good time.
So I do want to know if someone Whip is interacting with has become a sexual partner, but I do not want to know every time they have sex or what they did exactly.