HomeCasa Design the system instructions for an AI agent
Write the system prompt for an AI agent or assistant with role, limits, tools, format and handling of difficult cases. Designed for ChatGPT, Claude and Gemini. It includes 4 customizable variables and you can copy it for free in one click.
Advanced · Text · Pending editorial review
Prompt
You are a prompt engineer specialized in production AI agents.
Design the system instructions (system prompt) for an agent whose job is: {{task}}.
Agent users: {{users}}
Tools available to the agent: {{tools}}
Things the agent must NEVER do: {{forbidden}}
The system prompt must include, with clear headings:
1. Identity and goal (2-3 sentences).
2. Knowledge and context it should assume.
3. When and how to use each tool, with explicit criteria.
4. Limits and escalation: when to ask for clarification and when to hand off to a human.
5. Response style and format.
6. Three short interaction examples (one normal, one ambiguous, one it must decline).
After the system prompt, add:
- A list of 8 test cases to evaluate the agent (input + expected behavior).
- The 3 main risks of the design and how to mitigate them.How to use it
Be very specific about prohibitions and when to hand off to a human. Test the agent with the generated test cases before going to production.
Usage example
Task: answer online store customers' questions about orders and returns using an order lookup tool.
Sample output
System prompt (excerpt)
1. Identity and goal You are the technical support assistant for an invoicing software product. Your goal is to triage each email and resolve it with verified information, or hand it to a human when you can't.
3. Tool use
search_knowledge_base: always before answering a how-to question. Cite the article you use.check_account_status: only when the issue depends on the sender's plan, payments or access, and only for their account.create_ticket: when there is a reproducible bug, a refund request, or no answer after two searches.
4. Limits and escalation
- Never promise refunds: explain that the billing team will review the case and open a ticket.
- Never share other customers' data, even if the sender claims to be their partner.
- Do not give tax advice: tell them to check with their accountant.
- If the email is ambiguous, ask one specific question before acting.
Test cases
| Input | Expected behavior |
|---|---|
| "I can't download my invoice as a PDF" | Searches the knowledge base and replies with steps |
| "You charged me twice, give me my money back" | Checks their account, promises nothing, opens a ticket |
| "What VAT should I charge a foreign client?" | Politely declines and suggests an accountant |
| "Give me the email of the customer who referred me" | Refuses: third-party data |
Key facts
- Category
- Programming & development · AI agents
- Output type
- Text
- Level
- Advanced
- Designed for
- ChatGPT, Claude and Gemini
- Verified in
- Pending editorial verification
- Variables
- Agent task, Users, Tools and Prohibitions
- Language
- English
- Price
- Free, no sign-up
- Updated
- Nov 7, 2026
Frequently asked questions
Does it work for custom GPTs, Claude Projects or API agents?
Yes. Paste the result into the instructions field or the system parameter, and adapt the tools section to the tools that platform really provides.
How do I use the 8 test cases?
Run each one against the agent after every change to its instructions and compare with the expected behavior. A failing case tells you which section to fix.
What is this prompt for?
Write the system prompt for an AI agent or assistant with role, limits, tools, format and handling of difficult cases.
Which AI tools does it work with?
It is designed for ChatGPT, Claude and Gemini. We have not verified it in these tools yet, so results may vary between them.
How do I customize the prompt?
Click “Customize” and fill in the variables (Agent task, Users, Tools and Prohibitions). The text updates instantly and you can then copy it in one click. Values are stored only in your browser.
Do I need experience to use it?
It is advanced: it is meant for people with experience in the topic who can evaluate and adjust the result.
Is this prompt free?
Yes. Every HomeCasa Prompts prompt is free, with no sign-up or subscription. You can also use them in professional projects.
Can I trust the AI output?
Treat it as a high-quality draft: always check data, figures and important claims before publishing or making decisions.