What's cool is...

You are cool!

I don't know you, and I can still say that! It would be rude of me to insincerely flatter you by calling you attentive, or thoughtful, or kind, or intelligent, or anything like that at all. Really, it'd be the most disingenuine thing I can do. All I need to know about you to call you cool is that you are human. You are cool just because you exist. You don't need to do anything specific to be cool!