How to give AI a role (and why 'expert' isn't enough)
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“Act as an expert” might be the most copied line in prompt history. It’s also one of the least useful. An expert in what? For whom? With what priorities? Left undefined, the AI defaults to a generic expert and gives you a generic answer.
Why roles work
Language models learned from people who write very differently: nurses, lawyers, marketers, engineers, teachers. A specific role tells the model which of those voices to channel. It changes the words it uses, what it assumes you know, and what it flags as important.
Ask a tax accountant and a growth marketer how a small business should spend $5,000, and you’ll get two sensible but very different answers. The role decides which one you get.
The formula
A strong role usually has four parts:
- Specialty: what they do. “UX writer,” “data analyst.”
- Experience: how long, or at what level. “Senior,” “with 10 years of experience.”
- Audience or niche: who they serve. “For independent bookstores,” “for early-stage nonprofits.”
- Priority: what they care about most. “You favor plain language over jargon.”
You won’t always need all four, but each one narrows the target.
Weak vs. strong
| Task | Weak role | Strong role |
|---|---|---|
| Cold email | You are a sales expert | You are a B2B sales copywriter who writes short cold emails for agencies; you value one clear ask per email |
| Landing page | You are a developer | You are a senior front-end developer who builds fast, accessible landing pages and explains each step to non-coders |
| Reading a lease | You are a lawyer | You are a tenant-rights paralegal who explains leases in plain English and flags clauses worth checking with an attorney |
| Exam prep | You are a teacher | You are a high school chemistry teacher who uses kitchen analogies and quizzes me before moving on |
Roles for bots and assistants
When you’re writing instructions for a customer-facing bot, the role is its identity: “You are the virtual assistant for Maple Street Bakery: warm, quick, and helpful.” Add the brand’s tone and what the bot is not: “You never pressure customers to buy.” See how to write a system prompt for a customer service bot.
Common mistakes
Conflicting roles. “You are a gentle mentor and a brutal critic” pulls in two directions. Pick one, or say when each applies.
Flattery instead of detail. “You are the world’s best programmer” adds no information. Specifics beat superlatives.
A great role with no context. The role says who’s answering. The context says what situation they’re answering about. You need both.
Can’t decide on a role?
Ask yourself: if I could hire one person for this, who would it be? That’s your role. The coach suggests three roles tailored to your type of task, so you can pick one or write your own.