Can't tell if LP's are stereo or mono from ads

One of my pet peeves is finding an LP I want to buy but can't tell if it is stereo or mono. Bought a few that I thought were stereo but were not. Some sellers are reluctant to tell you if asked. As we all know, to get the best reproduction from either, the right play back equipment is essential. Further, equipment listings leave little doubt on this issue. This seems to be a common problem at Audiogon and Ebay. Can we get them to insist LP's are properly identified? Your thoughts.