There should be a box, say on the character screen, that gives you a list of all the took functions you have available. It could have the numbers where : Wood sawing: 1 (2) where the normal number is what i have in my inventory, and the () number is provided by either a tool on the ground, or from a vehicle.
What do you need it for?
it would be more of a comfort of life feature. It would be so I can just open my character sheet and Bam, know exactly what tool functions i have.