How do you make it so click detectors work while holding a tool?

I do understand that you have to put the script inside the tool but I just don't understand how to do it. when searching up on YouTube, all it says is "how to make ClickDetector script".

For example, lumber tycoon 2.... When you hold your axe and click a tree it does something, how do I do this? I don't mean how to remake lumber tycoon 2, I just want to know how to make a clickdetector work inside a tool basically.