Tools are systems living organisms use to do work. There are tools made by living organisms themselves and there are entities made by nature that living organisms use as tools. Automobiles and spaceships are examples of the former while a carmel helping a human to carry his load over a long arid distance and a horse ploughing the farmland of a farmer are examples of the latter. The basic reason for the use of tools is to reduce the burden of work. Tools are also used to enhance survival. For example, all medicines are tools used to enhance survival.
The form-function duality of tools is a system-work duality. In other words, the form of a tool is a system and its function is the work it expresses. Good tools have forms that optimize their functions.