Tip your hand
Definition 1 of 1
Pro Tip 1/3Strategic Use
Use the phrase to describe a situation where someone might reveal plans or strategies inadvertently. 
In negotiations, it's important not to tip your hand too early.
Pro Tip 2/3Avoid In Poker
In poker or similar games, avoid using it literally; it's a figurative phrase for non-gaming contexts. 
He has a poker face; you cannot tell if he's about to tip his hand.
Pro Tip 3/3Unintentional Disclosure
It focuses on revealing information you meant to keep secret, usually by mistake. 
Sarah tipped her hand when she mentioned the surprise party.