A tool is simply an object that enables someone to do something more efficiently. People have resorted to using these tools for self defense as an equalizer. It does give someone who knows how to use it a lot of power, but it doesn’t mean there aren’t glaring limitations to them.
For example, a tool does nothing if the person is not willing to use it. In addition, it does not give someone more physical strength, so it can be disarmed if you are not fast enough to react or strong enough to resist. In this case it can be used against you. Regardless, a tool should should not be a replacement to getting actual physical ability.