Job descriptions that sound like you

Job descriptions are one of the few documents where copying an average of everyone else's is the default, and where doing so actively costs you. The people you most want to hire read a lot of them and can spot boilerplate in a paragraph.

Upload the roles you have already written

Put your existing job descriptions in Documents, including the ones for roles you filled well. Those are the evidence of how your company describes work.

If you have never written one you were happy with, upload two you liked from elsewhere and say so. The employee will imitate what it is given, so be deliberate about what that is.

Give it the brief, not the job title

The common failure is asking for "a senior designer job description", which can only produce a generic one. What makes a role specific is the part that is awkward to write.

Write a job description for a Senior Designer, using our existing roles in
Documents as the model for structure and tone.

The specifics:
  they will own brand work for two or three retained clients
  they will present to clients themselves, which not every designer wants
  we are small, so there is no art director above them
  salary band is [X to Y]

Say the awkward parts plainly rather than dressing them up. If someone would
hate presenting to clients, I want them to work that out from the advert
rather than from the second interview.

Do not include a responsibilities list of more than six items, and do not
write a requirements list of things we would actually flex on.

"Do not list requirements we would flex on" is the instruction that changes who applies. Every unnecessary "must have" filters out people you would have hired, and it filters asymmetrically: the candidates most likely to self-reject on a soft requirement are the ones with the least to prove. Writing only what is genuinely required is the cheapest change you can make to a pipeline.

Read it as the candidate, not as the hiring manager

You will read it checking that it is accurate. Read it once more asking whether you would apply, and specifically whether you could tell what the first three months would actually be like.

If you cannot, the brief was thin rather than the writing.

Keep the good ones

A description you were happy with goes back into Documents. The next role is written from a slightly better model, and the voice converges rather than drifting.

What good looks like

The advert says the awkward thing out loud, has six responsibilities rather than fourteen, and reads like it was written by someone who has done the job.

The honest measure is at first interview: are you spending it correcting expectations the advert set wrongly? If so, the description was written for your convenience rather than the candidate's understanding.