When you click on a game, it does say either game only or case instructions and game. Prices aren't the best though.
When you sell a product, it should be readily apparent what condition it's in. "Complete" and "cartridge only", sorry to say, are mutually exclusive, and therefore should be used only where they apply.
It's gotten to where, if I see a game with a good price but the photo is stock/box art, I don't even click on it. That's probably my mistake, but I don't feel like wading through the arbitrary seller text & pointless graphics, only to be met with the words "complete with cartridge only".