A job description will help you stay crystal clear about who is the right candidate. Prepare it early in the process and share it with your team. It will save you lots of time, money, and help avoid unnecessary misunderstandings.
A job description helps you clarify the objective of the role and skills required.
Stay realistic about your needs (maybe it is an experienced developer rather than a CTO that you need?), requirements about the candidate (perfect candidates don’t exist) and what you can offer.
A job description facilitates your communication with the candidate and hiring team.
Not only do you want to make sure that the candidate is absolutely clear about the scope and challenges of the role, but a job description will also keep your hiring team on the same page regarding competencies and skills for assessment.
A job description is an internal document and as such does not need to advertise the role to a candidate.
It is an excellent checklist before you decide to hire the candidate. You can also use it later on for evaluation of your hiring process.