From Merriam-Webster:
tool
noun \ˈtül\
1
a : a handheld device that aids in accomplishing a task b (1) : the cutting or shaping part in a machine or machine tool (2) : a machine for shaping metal : machine tool
2
a : something (as an instrument or apparatus) used in performing an operation or necessary in the practice of a vocation or profession <a scholar's books are his tools>