The expression "bats in belfry" typically means that someone is behaving erratically or seems somewhat crazy. The antonyms for this phrase would likely involve terms that describe someone who is grounded, rational, and level-headed. Some possible antonyms could include words like focused, sensible, rational, organized, clear-headed, sharp-witted, and stable. These terms describe someone who is thinking logically, making informed decisions, and capable of keeping emotions in check. By contrast, bats in the belfry suggest chaos, confusion, and a lack of control. Therefore, the antonyms for this phrase imply the opposite - order, control, and a clear mind.