Job descriptions are important. They are not specifically required by law or regulation. However, the essential functions of a job must be considered in many contexts such as questions involving disability status or leave.
Job descriptions allow the employer to clarify what responsibility an employee has within the business and how the employee is expected to operate. This information matters from the first interview through the end of employment. Descriptions allow the employer to define relationships and obligations between co-workers and departments or divisions. They can set out educational, training, and skills requirements. They can also be the first place an employer looks to consider coaching, counseling, or evaluation. This information helps the employer evaluate performance for different positions too. Likewise, descriptions tell employees what is expected and serve as a form of communication to outline accountability.