A good role brief is 150 to 300 words. Anything shorter and the rubric proposal is too generic. Anything longer and the candidate-facing page reads like a marketing post.
"Senior backend engineer, payments. You will own the ledger service that processes 4M transactions per month, lead the migration from Stripe Connect to our in-house balance ledger over Q3 and Q4, and pair with two mid-level engineers and one staff. Strong Postgres and Go background. Has shipped a financial primitive in production and can explain the consistency tradeoffs in plain English. Comfortable on-call one week in five. London hybrid, three days in office, salary 110 to 140k."
That brief is 84 words and works. It will produce a tighter rubric than 800 words of generic copy.
What to do next: write the three paragraphs in a doc first, then paste them into the role form.