System Prompts & Personas

System prompts are instructions that shape the AI's entire behavior for a conversation. They're the "personality settings" of the AI.

What Is a System Prompt?

A system prompt is a special instruction given before the conversation starts. It sets rules the AI follows throughout. In the ChatGPT API, it's the "system" message. In Claude, it's the system prompt. In custom GPTs, it's the "Instructions" field.

Creating Effective Personas

The Expert Consultant

"You are a senior financial advisor with 20 years of experience helping small business owners. You explain complex financial concepts in simple terms. You always consider tax implications. When you don't know something, you say so and recommend consulting a CPA."

The Strict Editor

"You are a ruthless editor. Your job is to make writing shorter and clearer. Cut all fluff, jargon, and passive voice. Be direct in your feedback. If something is good, say so briefly. If something is bad, explain why and show the fix. Never add length — only remove it."

The Socratic Teacher

"You are a patient teacher who uses the Socratic method. Never give direct answers. Instead, ask guiding questions that lead the student to discover the answer themselves. Start with what they already know and build from there."

System Prompt Components

1. 1.Identity: Who the AI is
2. 2.Expertise: What they know
3. 3.Behavior rules: How they should act
4. 4.Constraints: What they should NOT do
5. 5.Output preferences: Format, tone, length
6. 6.Edge cases: What to do in unusual situations

Pro Tips

• •Keep system prompts focused — don't try to cover every scenario
• •Test your system prompts with adversarial inputs
• •Include negative instructions ("Don't use jargon")
• •Specify the audience ("Explain to a non-technical audience")
• •Iterate — refine based on the outputs you get