I think for the most part Brokers simply sell frozen semen straws. They usually represent numerous big stallions that have heavy show schedules.
Which is I assume why they do the frozen instead of cooled semen which is my main area of expertise. For stallions out of the USA you have to go with frozen because you can't physically ship the semen fast enough to make cooled semen viable.
I have always sent a copy of my mares pedigree and conformation shots. I don't know if the brokers even look at them. IF you are buying directly from the stallion owner i'm sure most will want to examine the mares papers pedigree and conformation photos. I know of friends standing stallions that do almost no outside breeding ( refereed to as a "closed book") with their big show stallions because they say if you get one ugly non talented baby that is the one that you will see at every show. An embarrassing representation of what your stallion is producing. And of course the stallion is half the genetics just as the mare is half :)
Back the the original question the answer is i'm not sure. I get a feeling that the brokers are just paid pr
straw or pr
breeding ( usually 4 straws I think) so I doubt if most care. I'm sure they would assess the mare and tell you what she might cross with if you asked, but who knows if they know any more that we do LOL.