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System Prompt Builder

Build structured system prompts for LLMs with guided sections for identity, rules, and boundaries

Quick Templates

Identity

Tone & Personality

Guidelines & Rules

1. Be concise and clear in your responses.

Boundaries & Restrictions

Advanced (Optional)

Generated System Prompt

~32 tokens
You are a helpful AI assistant.
Communicate in a professional manner.

## Guidelines
1. Be concise and clear in your responses.

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What is a System Prompt?

A system prompt is the foundational instruction set given to large language models (LLMs) like ChatGPT, Claude, Gemini, or Llama that defines how the AI should behave, respond, and interact with users. Unlike user messages, system prompts are typically hidden from end users and act as the "programming layer" that shapes the AI's personality, knowledge boundaries, and response patterns.

Think of a system prompt as the job description and training manual for an AI assistant. It tells the model who it should pretend to be, what it should and shouldn't do, how it should communicate, and what format its responses should take. A well-crafted system prompt is the difference between a generic chatbot and a specialized, reliable AI assistant.

Why System Prompts Matter

System prompts are critical for building production-ready AI applications. Here's why they're essential:

  • Consistency — Without a system prompt, AI responses can be unpredictable. A good system prompt ensures consistent behavior across all interactions.
  • Safety — Boundaries prevent the AI from providing harmful, inappropriate, or off-topic responses.
  • Brand Voice — System prompts let you control tone, personality, and communication style to match your brand.
  • Accuracy — By specifying expertise areas, you can improve the relevance and accuracy of responses.
  • User Experience — A well-prompted AI feels more natural and helpful, improving user satisfaction.

How to Use This System Prompt Builder

  1. Start with a template or blank slate — Use one of our pre-built templates (Customer Support, Code Assistant, Writing Coach) as a starting point, or begin fresh.
  2. Define the AI's identity — Who is this AI? Be specific. Instead of "helpful assistant," try "senior software engineer with 15 years of Python and cloud infrastructure experience."
  3. Specify areas of expertise — List the domains the AI should be knowledgeable about. This helps the model focus its responses.
  4. Choose a communication tone — Select from professional, casual, technical, empathetic, or other tones that match your use case.
  5. Add behavioral guidelines — These are the "do's" — numbered rules that tell the AI how to behave. Keep them specific and actionable.
  6. Set clear boundaries — These are the "don'ts" — topics, actions, or behaviors the AI should avoid. Boundaries are often more important than guidelines.
  7. Configure output format — If you need responses in JSON, markdown tables, or other specific formats, define them here.
  8. Add examples — Few-shot examples help the AI understand exactly what you expect.
  9. Copy and deploy — Once satisfied, copy your prompt and use it in OpenAI, Anthropic, or any LLM API.

Best Practices for Effective System Prompts

1. Be Specific, Not Vague

Vague instructions lead to inconsistent behavior. Instead of "be helpful," specify exactly how to help: "Provide step-by-step explanations with code examples for programming questions."

2. Use Numbered Lists for Rules

LLMs follow numbered rules more reliably than prose. Structure your guidelines as a numbered list for better adherence.

3. Prioritize Boundaries Over Guidelines

What the AI should NOT do is often more important than what it should do. Place restrictions prominently and make them explicit.

4. Include Examples (Few-Shot)

Showing is better than telling. Include 2-3 example exchanges to demonstrate expected behavior.

5. Test and Iterate

No prompt is perfect on the first try. Test with real queries, find failure cases, and refine your prompt iteratively.

6. Keep It Focused

Don't try to cover every edge case. A focused, concise prompt often outperforms a lengthy, complex one.

Common Use Cases for System Prompts

Customer Support Bots

Automate Tier 1 support with AI that knows your product, follows escalation protocols, and maintains brand voice.

Coding Assistants

Build specialized programming helpers that follow your team's coding standards and best practices.

Content Creation

Create AI writers that match your brand's tone, style guide, and content requirements.

Internal Knowledge Bases

Build AI assistants that help employees navigate company policies, documentation, and procedures.

Frequently Asked Questions

How long should a system prompt be?

There's no perfect length. Focus on clarity and completeness. Most effective system prompts range from 200-1000 tokens. Include what's necessary, but avoid redundancy. Longer isn't always better — concise prompts often perform as well or better than lengthy ones.

Can users override system prompts?

Users can attempt to override system prompts through "jailbreaking" or prompt injection attacks. While no system prompt is 100% secure, strong boundaries, explicit refusal instructions, and monitoring can significantly reduce this risk. Consider using our Injection Tester tool to identify vulnerabilities.

Should I include examples in my system prompt?

Yes, whenever possible. Few-shot examples (2-3 sample interactions) are one of the most effective ways to guide AI behavior. They show rather than tell, reducing ambiguity and improving response quality.

Do different LLMs require different prompts?

Generally, a well-written system prompt works across models (GPT-4, Claude, Gemini). However, each model may interpret instructions slightly differently. It's best to test your prompt on your target model and make adjustments as needed.

How do I make my AI refuse certain topics?

Use explicit boundary statements. Instead of hoping the AI won't discuss a topic, add clear instructions like: "You must not provide medical diagnoses. If asked, politely explain that users should consult a healthcare professional." Be specific about what to refuse and what to say instead.

Related Tools

  • • Role Generator — Generate expert role definitions for your system prompts
  • • Prompt Injection Tester — Test your prompts for security vulnerabilities
  • • Prompt Version Tracker — Track changes and compare prompt versions
  • • Few-Shot Builder — Create effective example interactions for your prompts