Under EEOC rules for the Americans with Disabilities Act, what an employer puts in a job description is considered the primary determinant of what the essential functions of that position are. That, in turn, helps the employer deal with any ADA claims that might come about in the future, in case the question is whether an applicant or employee is able to perform the essential functions of the job with or without reasonable accommodation.
A good job description makes it much easier to deal with an unemployment claim if the work separation occurred because of a claimant's refusal or failure to perform the functions of the position. In a quit case, if the employee was aware of what the job involved prior to taking it, and later quits rather than do the agreed-upon job, the claimant would not have a good argument at all for claiming that he or she had good work-connected cause for quitting. In a discharge case, failing to do one's job can lead to a judgment of various forms of misconduct, including insubordination, avoidable negligence, failing to follow instructions, failing to do one's best, and so on.
A good job description makes it much easier to measure an employee's performance and hold him or her to known standards, which is important for promotions, job transfers, raise reviews, and corrective action.
Any good job description will be specific enough to accurately describe the job in question, yet flexible enough to include other duties as assigned. The company should make it clear to all employees that when the needs of the company or its customers dictate, their jobs will entail whatever needs to be done that is assigned by a supervisor and is within the employee's capacity to deliver.
Be sure to include the requirement that part of each employee's job is to work the assigned schedule and comply with the company's timekeeping policy.
For some assistance with developing job descriptions, visit the following websites:
The sites linked there will help an employer get started, but most of the detail in a particular job description will be supplied by the supervisor of the position in question and by the experienced employees who are already performing that job.
Go to the Employer Commissioner's Page
Go to the TWC Home Page