When writing your job descriptions, focus on results. Clearly lay out the critical functions that must be done. Use action verbs to indicate the activity that the employee will be expected to perform. Employees are more confident in their abilities to perform the job when they are fully aware of what is expected of them. If they don't clearly know what's expected of them, you're not really giving them a chance to perform at the level for which they were hired.
Job descriptions are a great management tool as well.
Your human resources department can use them to initially screen applicants. They can help your human resources department assess whether or not an applicant is even qualified for the job by verifying if his or her resume or application match up with the required education, licensing, certifications, skills, or experience listed on the job description. Management can use the job descriptions to help them determine standards for measuring levels of performance. They can also serve as a way to decide appropriate compensation for the work and for the level of performance delivered. Good and clear communication between you and your employees should be your goal.