Useful roles, clear goals and success criteria

Roles: useful, but not magic

A role (sometimes called a persona) tells the model which perspective, vocabulary and priorities to use: "You are an experienced primary-school teacher", "Act as a careful copy-editor", "Review this as a sceptical investor would."

Roles help most when they bring a specific way of looking at the task:

• Reviewer roles surface problems: "As a strict accessibility reviewer, list barriers in this event invitation."
• Audience roles test clarity: "Read this as a new employee on their first day. Which terms would confuse you?"
• Expert vocabulary sets the register: "Explain as a nurse would to a patient's family."

What a role does not do: it does not give the model qualifications, access to new information or accountability. "You are a world-class lawyer" does not make the output legal advice, and the model may sound more confident without being more correct. Treat role-play output with the same scepticism as any other output.

A role is decoration when it changes nothing: "You are a helpful assistant who writes emails" adds little to "Write an email". Keep roles that change perspective; drop the rest.

Goals: say why, not only what

The goal is the outcome the output should serve. Stating it lets the model make sensible choices you did not spell out.

• Task only: "Summarise this report."
• Task + goal: "Summarise this report so that the board can decide in five minutes whether to fund phase two."

With the goal, the model knows to prioritise costs, risks, results and a recommendation over background history.

Success criteria: define "good" in advance

Success criteria are the standards the output must meet. Writing them before you see the output protects you from accepting the first plausible answer. Good criteria are:

• Observable — you can check them by reading the output ("each option includes a cost estimate").
• Relevant — tied to the goal, not to style preferences that do not matter.
• Few — three to five criteria are usually enough.

Example for a product description:

1. Mentions the three features in the spec sheet, and no others.
2. Under 90 words.
3. No claims about health benefits.
4. Ends with the delivery time from the spec sheet.

You can put the criteria in the prompt and use them afterwards as a checklist — the same list serves both. This is the seed of the evaluation rubrics you will build in Module 9.

Putting it together

Role: You are an experienced volunteer coordinator reviewing a recruitment post.
Goal: Help us attract reliable weekend volunteers for a food bank.
Task: Rewrite the draft post below.
Success criteria:
- States the time commitment (one Saturday morning a month) in the first two sentences.
- Explains what volunteers actually do in three bullet points.
- Friendly, plain language; under 150 words.
- Ends with how to sign up (email address from the draft).
Draft:
"""
(paste draft)
"""