think on one's feet

Part of the skill involved is being able to think on one’s feet and make those objections in a timely and accurate way to preserve them for appeal.

These interjectory phrases allude to the inability to concentrate or think on one’s feet.

“A phone scam is much more dangerous because one has to think on one’s feet,” he says.

It is best to jot down bullet points and remain flexible enough to think on one's feet, says Fox.

There is a suggestion of the unscrupulous when the expression is used in a political context, though in terms of business deals it does not normally denote anything more sinister than the ability to act quickly and think on one's feet.