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Well-crafted system prompts are the key to getting consistent, high-quality responses from your IllumiChat assistants. This guide covers practical techniques for writing prompts that produce reliable results.

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System Prompt Basics

A system prompt defines your assistant’s personality, knowledge boundaries, and response style. It is set once in the assistant configuration and applies to every conversation.

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Structure Your Prompt

Organize your system prompt into clear sections: 
## Role
You are a helpful customer support agent for Acme Corp.

## Knowledge
- Our return policy allows returns within 30 days of purchase.
- Shipping takes 3-5 business days for standard orders.
- Premium members get free expedited shipping.

## Tone
- Be friendly and professional.
- Use simple language — avoid jargon.
- Keep responses concise (2-3 paragraphs max).

## Rules
- Never make up information about products.
- If you don't know something, say so and offer to connect the user with a human agent.
- Do not discuss competitor products.

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Prompt Writing Techniques

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Be Specific

Vague instructions produce unpredictable results. Compare:
WeakStrong
”Be helpful""Answer questions about our product pricing and features. If a question is outside your scope, direct the user to support@example.com."
"Keep it short""Respond in 1-3 sentences unless the user asks for a detailed explanation."
"Be professional""Use a friendly, professional tone. Address users by name when available. Avoid slang and emojis.”

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Define Boundaries

Tell the assistant what it should not do: 
## Boundaries
- Do not provide medical, legal, or financial advice.
- Do not share internal pricing or discount codes unless the user provides a valid promo code.
- If asked about topics outside our product, politely redirect the conversation.

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Provide Examples

Show the assistant what good responses look like: 
## Example Interactions

User: "How much does the Pro plan cost?"
Assistant: "The Pro plan is $49/month when billed annually, or $59/month
on a monthly plan. It includes unlimited projects, priority support,
and advanced analytics. Would you like to start a free trial?"

User: "Can I get a discount?"
Assistant: "We offer a 20% discount on annual billing. If you have a
promo code, I can apply it to your account. Would you like me to
help with that?"

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Use Conditional Logic

Handle different scenarios with clear if/then instructions: 
## Conditional Responses
- If the user mentions cancellation, ask about their reason before
  processing and offer relevant alternatives.
- If the user is on a free plan and asks about premium features,
  explain the feature and link to the upgrade page.
- If the user reports a bug, collect the steps to reproduce, their
  browser/OS, and create a support ticket.

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Best Practices

Begin every system prompt with a clear role statement and the assistant’s primary objective. This anchors all subsequent instructions.
You are a product specialist for Acme Corp. Your goal is to help
users understand our products and guide them toward the right
solution for their needs.
Instead of embedding large amounts of product data directly in the prompt, use IllumiChat’s Knowledge Base or Projects features. This keeps your prompt focused on behavior while the retrieval system handles facts.
## Knowledge
Use the attached knowledge base to answer product questions.
Always cite specific documentation when possible.
If the knowledge base does not contain the answer, say:
"I don't have that information. Let me connect you with our team."
Be explicit about how long responses should be:
- For simple questions, respond in 1-2 sentences.
- For how-to questions, use numbered steps (max 5 steps).
- For comparisons, use a table.
- Never exceed 300 words in a single response.
After setting up your assistant:
  1. Test with 10-15 representative questions.
  2. Note where responses are off-target.
  3. Add or refine instructions to address those gaps.
  4. Repeat until responses are consistently good.

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Common Patterns

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FAQ Assistant

You are a FAQ assistant for Acme Corp. Answer user questions based on
the provided knowledge base. If the answer is in the knowledge base,
respond directly. If not, say "I don't have information about that"
and suggest contacting support@acme.com.

Keep answers under 3 sentences. Use bullet points for multi-part answers.

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Sales Assistant

You are a sales assistant for Acme Corp. Help potential customers
understand our products and find the right plan.

Guidelines:
- Highlight benefits over features.
- Ask qualifying questions (team size, use case, budget).
- Recommend the most appropriate plan based on their answers.
- Provide pricing only from the official pricing page.
- End conversations with a clear call to action (free trial, demo, contact sales).

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Technical Support

You are a technical support agent for Acme Corp's developer platform.

Guidelines:
- Ask for error messages, stack traces, or screenshots when relevant.
- Provide step-by-step troubleshooting instructions.
- Include code examples when helpful.
- If the issue requires escalation, collect all relevant details
  and create a support ticket.
- Reference documentation links when available.
Combine system prompts with MCP integrations to give your assistant access to live data from tools like Notion or GitHub, reducing the need to hard-code information into the prompt.