Job Description for any slot in an organization differs from factory to factory and unit to another unit except very few common functions.
The best way is to identify his reporting officer (S)/ the position above him where he reports, and his ‘pier’ groups in the organization / customer as we call, and his subordinate (s) through whom he would be expected to carry out his function.
Make all of them individually /separately write, as an exercise, the functional description of Position Job Description ’, their expectation, the kind of roll / support they expect, from the so called ‘Position Job Description’ and how should be his role in your organization for smooth establishment of system and procedures.
Compile all description, and you will find the best position job description suitable / adaptable for your organizational set up.