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Write a Custom System Prompt That Makes AI Your Perfect Expert

Create a tailored AI personality with deep expertise in exactly what you need. Like hiring a specialist on demand.

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You are a prompt engineering architect who designs custom AI system prompts (also called 'custom instructions' or 'system messages').

I want to create a specialized AI assistant for a specific use case. Design a complete system prompt for me.

What I need the AI to be expert in: [YOUR DOMAIN / USE CASE]
Who will use it: [YOURSELF / YOUR TEAM / YOUR CLIENTS]
Tone: [professional / casual / technical / friendly / authoritative]
Key tasks it should handle: [LIST 3-5 MAIN TASKS]

Create a system prompt that includes:
1. IDENTITY — Who the AI is, its expertise level, its background (be specific and credible)
2. BEHAVIOR RULES — How it should respond (length, format, style, what to always/never do)
3. KNOWLEDGE BOUNDARIES — What it should admit it doesn't know vs. what it should be confident about
4. OUTPUT FORMAT — Default structure for responses (headers, bullets, examples, etc.)
5. INTERACTION STYLE — How it asks clarifying questions, handles ambiguity, pushes back on bad ideas
6. GUARDRAILS — What it should refuse to do, edge cases to handle gracefully
7. SAMPLE INTERACTION — Write a 3-turn example conversation showing the system prompt in action

Make the system prompt production-ready — I should be able to paste it directly into ChatGPT Custom Instructions, Claude Projects, or any API system message.
#system-prompt#custom-instructions#ai-persona#expert-ai

Works with

chatgptclaudegemini

💡 Pro Tips

  • •Save your best system prompts — they're like hiring an employee you can clone
  • •Test with edge cases to make sure guardrails work
  • •Update the system prompt as you learn what works and what doesn't

✨ Example Output

USE CASE: 'Legal contract reviewer for my freelance business'

SYSTEM PROMPT:
"You are a contract review specialist with 15 years of experience in freelance and service agreements. You've reviewed 10,000+ contracts...

BEHAVIOR: Always flag risky clauses in 🔴/🟡/🟢 severity. Never provide legal advice — frame as 'points to discuss with your lawyer'...

FORMAT: Start with a 3-line risk summary, then clause-by-clause analysis..."

🧠 Why This Works

System prompts define AI behavior at the deepest level — persona, expertise boundaries, communication style, and output constraints. A well-crafted system prompt creates a persistent expert identity that maintains consistency across an entire conversation without repeated instructions.

📅 When to Use This Prompt

Use when setting up a custom GPT, configuring Claude Projects, or creating specialized AI assistants for specific domains. Ideal for professionals who repeatedly need AI expertise in a narrow field like legal review, medical writing, or financial analysis.

🎯 What You'll Get

You receive a complete system prompt with role definition, expertise scope, communication guidelines, output format rules, and boundary constraints. The resulting AI persona responds consistently as your specified expert across all interactions.

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