"I'd like to buy a new boomerang please. Also, can you tell me how to throw the old one away?"
Never mind whether you think that joke is funny. Do you think your best friend would like it?
You might think you know the answer; after all, people like each other partly because they make each other laugh. At the very least, you might be confident that a mere machine, equipped with data about how other people react to jokes, couldn't do better than you in answering the question of what your best friend will find funny.