Q: Are players required to show how many cards they have in their hand?

A: The number of cards in each player’s hand is supposed to be open information, so, while a player may wish to obfuscate how many cards they have, by stacking them, or trying to minimize their appearance, if directly questioned, they should give an accurate answer.

They may feel free to try to discourage you from taking or utilizing their cards, of course: “Yeah, I have a big hand, but my cards all suck…” for example. That’s allowed – it’s just opinion, of course.