Write the prompt as a brief for a capable colleague with no background

Anthropic's prompting guide puts it as a golden rule: show your prompt to a colleague with minimal context on the task and ask them to follow it. If they would be confused, the model will be too.

A good brief answers the questions a newcomer would ask:

• What is the task? What should be produced, and for whom.
• What does done look like? Length, format, fields, level of detail.
• What are the constraints? What must be included, what is out of scope.
• What happens at the edges? Missing data, ambiguous input, off-topic requests.

If you want more than the minimum, ask for it. The same guide notes that "above and beyond" behaviour has to be requested explicitly rather than inferred from a vague prompt.