be up to something

[be up to something] {v. phr.}, {informal} 1. To feel strong enough or knowledgeable enough to accomplish a certain task.

Are you up to climbing all the way to the 37-th floor?

Are we up to meeting the delegation from Moscow and speaking Russian to them?

2. Tendency to do something mischievous.

I'm afraid Jack is up to one of his old tricks again.