It depends. If you told a joke, then good. If you did something silly, then bad. "You crack me up" simply means "You make me laugh."

1. Definition make me laugh 2. Use “Crack me up” is a common and useful expression. It sounds much more natural to describe a funny person as someone who “cracks you up,” instead of someone who makes you laugh. The expression can be used in many ways, and all of them are related to laughter. Examples 1. ””Eddie Murphy cracks me up. He is so funny. I love his movies.”“ ””I was cracking up when you slipped and fell yesterday. I’m sorry for laughing, but you looked really funny. I hope you didn’t hurt yourself.”“ ””Dan was cracking me up last night. He knows so many great jokes.”“

I had the same doubt... Now i get it^^