tip your hand

tip (one's) hand

To reveal one's intentions, plans, secrets, or resources. An allusion to letting someone else see the cards one is currently holding (one's "hand"). The foreign leader has definitely tipped his hand when it comes to his country's position in the negotiations. Remember not to tip your hand when you go into the meeting.
See also: hand, tip
Farlex Dictionary of Idioms.

tip your hand (or mitt)

reveal your intentions inadvertently. US informal
This expression is the opposite of keep your cards close to your chest (see card).
1966 Martin Woodhouse Tree Frog We couldn't very well oppose it without tipping our hand.
See also: hand, tip
Farlex Partner Idioms Dictionary
See also:
  • beat (one) to the draw
  • Earth to (someone)
  • earth to someone
  • baton
  • hand on the baton
  • give (one) (one's) marching orders
  • give somebody their marching orders
  • give someone their marching orders
  • game is not worth the candle, the
  • get in/into one's hair, to
References in periodicals archive
(Note: if you're desperate to leave your current job, don't tip your hand, as it will weaken your position in negotiations.)
Closing the deal: it's OK to negotiate salary with a potential employer
You don't need to watch poker on TV to know that it's never wise to tip your hand.
Deal in the Red Sox at winter meetings
It's never a good idea to tip your hand before you have a genuine offer, the piece of paper that makes it a done deal.
When it's time to say goodbye. (Career Rx)
If you suspect that an employee is committing fraud, carry out a quick (and quiet!) check on your own, bearing in mind that too much digging may tip your hand and the perpetrator may destroy crucial evidence.
Is your business being defrauded?