| Claxon |
So it's very non-specific about what kind of tool it is.
I do not think I would allow it to do fine detail manipulation like lock-picking, at least not by default.
If you picked up the fighting horn feat which explicitly says you can change the size and shape of your horn with your mental powers I'd be open to a player changing their horn to be used as most any kind of tool.
By default I imagine it more like being a hammer, or crowbar type tool.