Many technicians have strong feelings about the tools they use. They like certain brands and dislike others, which is why most contractors leave the tool buying to the technicians themselves. That way, they can buy what they want, and they tend to take better care of tools they actually own.
To make sure technicians have the right tools for the job, contractors usually provide a list of required items they must own, such as screwdrivers, wrenches, pliers, refrigerant gauges, and the like, and they may offer a monthly allowance to help with those purchases. But tool policies vary from one company to the next, and most evolve over time, based on the needs of the particular business as well as the input from the technicians who work there.