JD should have the information belongs to employes work details, roles and responsibilities which he needs to do during the year of service cycle ( appraisal to appraisal ) this needs to be agree by employee and his immediate manager.
this needs to be review by his immediate manager on every Quarterly / half yearly and yearly base for employee appraisal.
JD needs to be designed/written by Project leader / process leader / project head for his team ( its vary process to process)
if you are a HR , u don't have to worry about this , keep this on process head / project head.
as a HR you needs to take this is base for employee appraisal.
Let me know if you have any questions.
2nd December 2011 From India, Madras