ESL job descriptions can be incredibly vague and you open yourself up to a lot of surprises if you don’t clarify what you’ll actually be teaching. Will it be grammar, literature, art, or some combination?
You should already know the required amount of teaching hours (if not – ask!) and now is the time to determine how they are allocated.
Things to look out for here are a mix of class types or subjects as that will almost certainly mean more prep work. Conversely, if you learn that you’re only teaching 2 different classes then a lot of your material can be reused, thereby saving you time and work.