when replying that way in any way, on text or actually just saying “cool”. my friends say cool a lot and I really don’t mind it and my partner says it too but some people have thought it was rude and I had a friend say “that’s what I say when I don’t give a damn”.
Then it’s context. If you’re going for the excited delivery, try throwing in a ! or a “That’s” beforehand otherwise it could be misinterpreted as uncaring or dismissive.