open (up) (one's) kimono
To be transparently open about one's plans, dealings, or intentions. I assure you that our company has opened our kimono about every aspect of our tax obligations to the state.
open (up) one's kimono
Sl. to reveal what one is planning. (From the computer industry, referring especially to the involvement of the Japanese in this field.) Sam isn't one to open his kimono much when it comes to new products. Even if Tom appears to open up his kimono on this deal, don't put much stock in what he says.