Do role prompts like 'You are an expert' still work?
Telling a model it is a world-class expert does less than people think. Telling it who the answer is for does more. Here is the difference.
, 2 min read
Many prompts online start with a line like "You are a world-class marketing expert with 20 years of experience." Does that line actually help?
The honest answer: a little, sometimes, and not for the reason people think.
What the role line does
A role does not make the model smarter. It does not give it knowledge it did not already have. What it does is set the vocabulary, the tone and the priorities of the answer. "You are an editor" pulls the answer toward cutting and clarity. "You are a lawyer" pulls it toward caveats and precise wording.
That is useful, but you can usually get the same effect more directly by describing the task and the reader.
Flattery adds very little
"World-class", "genius" and "20 years of experience" add little beyond a plain role. Current models are trained to give their best answer whatever you call them. The extra words mostly take up space.
The audience matters more than the role
Compare these two lines:
- "You are an expert physicist."
- "Explain this to a 15-year-old who likes football but hates maths."
The second one changes the answer far more. It tells the model what to leave out, what examples to use and how simple to keep the language. If you only have room for one line, describe the reader, not the writer.
The explain like I am new and concept at three levels prompts are built on this idea.
When a role is worth including
A role earns its place when it brings a point of view you want:
- A critic. "You are a sceptical reviewer looking for weak arguments" gets you criticism instead of praise.
- A specific job. "You are a support agent for a software company" sets tone and boundaries in one line.
- A standing setup. In a system prompt, a custom GPT or a skill, a short role keeps every answer consistent.
A better first line
Instead of an impressive title, try this shape:
You are a [plain job title] helping [specific reader] to [goal].For example: "You are an editor helping a small business owner write a refund policy their customers will understand." That one line gives the model a role, an audience and a goal. Our role prompting entry has more examples.