Writing Instructions & Persona

The instructions you write are the heart of your custom GPT. They tell it who to be, how to behave, and what to do. Let's turn your plan into effective instructions.

Accessing the GPT Builder

1. Go to chat.openai.com
2. Click your profile icon (bottom left)
3. Select "My GPTs"
4. Click "Create a GPT"

You'll see two tabs: Create and Configure. Start with Create for a guided experience, or jump to Configure for direct control.

The Instructions Field

In Configure mode, you'll find the Instructions field. This is where the magic happens. Your instructions should cover:

1. Identity: Who is this GPT?
2. Behavior: How should it act?
3. Tasks: What should it do?
4. Constraints: What should it avoid?
5. Format: How should it structure responses?

Writing Your GPT's Identity

Start by defining who your GPT is:

Example:

"You are PrepCoach, a friendly interview preparation specialist who helps job seekers practice and improve their interview skills."

Defining Behavior and Tone

Tell your GPT how to communicate:

Example:

"Be encouraging but honest. Keep responses concise unless the user asks for more detail. When users seem nervous, reassure them that practice makes progress."

Specifying Tasks

List exactly what your GPT should do:

Example:

"Your main tasks are:

1. Conduct mock interviews by asking one question at a time and waiting for responses
2. Provide specific, actionable feedback on each answer
3. Teach the STAR method (Situation, Task, Action, Result) when relevant"

Setting Constraints

Define what your GPT should avoid:

Example:

"Important boundaries:

• Do NOT write scripted answers for users to memorize
• Do NOT promise that following advice will guarantee a job
• If asked about salary negotiation, provide general tips but suggest researching market rates"

Formatting Guidelines

Tell your GPT how to structure responses:

Example:

"Response formatting:

• Use bullet points for feedback
• Structure each feedback response as: Strengths, Areas to Improve, One Tip
• Keep interview questions to one at a time"

Complete Instructions Template

Here's a full template to adapt:

Testing Your Instructions

After writing instructions:

1. Click "Preview" in the GPT Builder
2. Try common requests your users would make
3. Try edge cases to test boundaries
4. Refine based on what you observe

Common Instruction Mistakes

Mistake	Fix
Too vague: "Be helpful"	Specific: "Answer questions with step-by-step explanations"
Contradictory rules	Review instructions for conflicts
No personality	Add tone and communication style
Missing edge cases	Add "If X happens, then Y" rules

Key Takeaway

Great instructions are specific, structured, and complete. They define identity, behavior, tasks, constraints, and format. Don't worry about getting them perfect on the first try—you can always refine them after testing. Next, we'll add knowledge files to make your GPT even smarter.