Roles and Personas

Why Roles Matter

In the previous lesson, we explored anatomy of a prompt. Now let’s build on that foundation. “You are a helpful assistant.”

That’s the default. And it’s fine for simple questions. But for anything serious, it’s like hiring an employee with no job description—they’ll try to help, but they won’t know how.

A well-defined role completely changes AI behavior. Same underlying model, dramatically different outputs. The AI adjusts its vocabulary, expertise level, communication style, and even what it considers important.

This lesson teaches you to create personas that behave exactly how you need them to.

The Anatomy of a Persona

An effective persona has five components:

1. Identity

Who is this person?

You are a senior data scientist with 12 years of experience at Fortune 500 companies.

Not just “a data scientist.” Senior. Specific experience. The details trigger different response patterns.

2. Expertise Domain

What do they know deeply?

You specialize in customer churn prediction, A/B testing, and translating technical findings for executive audiences.

This scopes the AI’s focus. It’ll lean into these areas and acknowledge gaps in others.

3. Communication Style

How do they talk?

You communicate in clear, jargon-free language. You use concrete examples over abstract theory. You're direct but not dismissive.

This shapes tone, vocabulary, and structure.

4. Decision-Making Approach

How do they solve problems?

You start with clarifying questions before diving into solutions. You consider trade-offs explicitly. You flag risks early rather than burying them.

This affects how the AI structures its thinking.

5. Boundaries

What don’t they do?

You don't provide legal or medical advice. You don't speculate beyond your expertise. You don't pad responses with unnecessary caveats.

Boundaries prevent common failure modes.

The Expertise Dial

Think of expertise as a dial from 1 to 10:

The key insight: Different expertise levels give different answers to the same question.

Ask a novice-level persona “How do I improve my website’s SEO?” and you’ll get basics—keywords, meta tags, page speed.

Ask an expert-level persona the same question, and you’ll get nuanced discussion of search intent, topical authority, internal linking architecture, and how recent algorithm updates affect strategy.

Neither is wrong. Choose the level that fits your actual need.

Persona Template

Here’s a copy-paste template:

You are [ROLE] with [EXPERIENCE/CREDENTIALS].

Your expertise includes:
- [DOMAIN 1]
- [DOMAIN 2]
- [DOMAIN 3]

Your communication style:
- [TRAIT 1]
- [TRAIT 2]
- [TRAIT 3]

Your approach to problems:
- [APPROACH 1]
- [APPROACH 2]

You do NOT:
- [BOUNDARY 1]
- [BOUNDARY 2]

Three Worked Examples

Example 1: Technical Writer

You are a senior technical writer who has documented APIs for developer audiences for 8 years.

Your expertise includes:
- API reference documentation
- Code examples that actually work
- Progressive disclosure (simple first, complex later)

**Quick check:** Before moving on, can you recall the key concept we just covered? Try to explain it in your own words before continuing.


Your communication style:
- Precise but not pedantic
- Shows rather than tells (code over description)
- Assumes reader intelligence but not prior knowledge

Your approach:
- Lead with the most common use case
- Provide complete, runnable examples
- Anticipate "but what about..." questions

You do NOT:
- Write walls of text without code examples
- Use marketing language
- Assume readers know your product already

Example 2: Strategic Advisor

You are a business strategy consultant who has advised 50+ startups and helped 8 reach successful exits.

Your expertise includes:
- Go-to-market strategy
- Competitive positioning
- Knowing when to say "this idea won't work"

Your communication style:
- Direct and honest, even when it's uncomfortable
- Backs opinions with reasoning
- Asks probing questions before giving advice

Your approach:
- First understand the full context
- Consider what could go wrong, not just what could go right
- Provide options with trade-offs, not single answers

You do NOT:
- Tell founders what they want to hear
- Give generic advice that applies to everyone
- Pretend certainty you don't have

Example 3: Patient Teacher

You are a teacher who specializes in explaining complex topics to complete beginners. You've taught thousands of students who thought they "couldn't learn" technical subjects.

Your expertise includes:
- Breaking complex topics into tiny steps
- Finding relatable analogies
- Knowing exactly where students get confused

Your communication style:
- Warm and encouraging
- Uses everyday language, not jargon
- Celebrates small wins

Your approach:
- Start with WHY before WHAT or HOW
- Use concrete examples before abstract rules
- Check understanding frequently

You do NOT:
- Assume any prior knowledge
- Make students feel dumb for not knowing something
- Rush through foundational concepts

When Personas Go Wrong

Common mistakes:

Too vague:

“You are an expert.”

Expert at what? How do they communicate? What’s their approach? This barely constrains behavior at all.

Contradictory traits:

“You are a detail-oriented expert who gives brief, high-level overviews.”

Pick one. Detail-oriented and brief are in tension.

Persona doesn’t match task:

You define a casual, friendly persona then ask for a formal legal document.

The AI will struggle. Match persona to purpose.

Over-specified:

Two pages of character backstory and personality traits.

At some point, you’re writing fiction, not a functional persona. Keep it focused on what actually affects outputs.

Testing Your Persona

Here’s how to validate a persona works:

1. Ask the same question twice — Do you get consistent responses?
2. Ask something outside scope — Does the AI acknowledge limits?
3. Push for forbidden behavior — Does it hold boundaries?
4. Compare with no persona — Is the output meaningfully different?

If the answer to any of these is no, refine the persona.

Key Takeaways

• Personas shape multiple dimensions: tone, expertise, vocabulary, approach
• Use the five components: Identity, Expertise, Style, Approach, Boundaries
• Adjust the “expertise dial” based on your actual need
• Boundaries (what NOT to do) prevent common failures
• Test personas by checking consistency and limits

Next lesson: few-shot learning—teaching AI by example. This is where things get really powerful.