Job descriptions, job performance and pay go hand-in-hand. Employees are paid based on how well they perform a job. How well someone performs a job can't be determined without knowing the job responsibilities. So ultimately, a job description is the heartbeat of a job position. Accurate and thorough job descriptions serve a vital role in determining whether a position qualifies to be exempt from overtime, and also provides important information to employees' physicians in order for them to determine if an employee can perform the essential functions of job.