An effective job ad is not just a job description. It is a carefully crafted message with the aim of attracting the best qualified candidates for your job.
Think of your job ad like a funnel where initially you are casting the net out wide to a broad audience. Then, as the readers make their way through your carefully crafted advertisement, they are either self-ejecting from the process or they are mentally ticking all the boxes because they can actually picture themselves in the role. In the end you really only want a handful of suitable candidates to apply.