# System Prompt Generator

> Describe what your assistant should do, pick where it runs and its tone, and our AI writes a full system prompt with its role, rules, limits and reply format. Free.

Canonical: https://promptitin.com/free-tools/system-prompt-generator
Last updated: 2026-11-13

A system prompt tells an assistant who it is and how to behave in every chat. Say what yours should do and our AI writes the whole thing: role, rules, what to avoid and how to reply.

This is an interactive tool. Use it at https://promptitin.com/free-tools/system-prompt-generator.

## How to use it

1. Write the assistant's job in one line, like “answer customer questions for my yoga studio”.
2. Pick where it will run: a custom GPT, Claude Project, Gemini Gem, website chatbot or agent.
3. Pick a tone if it matters.
4. Tap Make my prompt, log in with one click, and paste the result into your assistant's instructions.

## Tips

- Say who the users are. An assistant for beginners should sound different from one for experts.
- Tell it what to do when it doesn't know. “Say so and suggest who to ask” beats a made-up answer.
- Fill in any [INSERT …] fields with your real details, like opening hours or prices.
- Test it with three awkward questions before you share it.

## FAQ

### What is a system prompt?

The standing instructions an AI assistant reads before every conversation. It sets the role, tone, rules and reply format, so users don't have to repeat them.

### Where do I paste the system prompt?

In a custom GPT, the Instructions box. In a Claude Project, the project instructions. In a Gemini Gem, the Gem's instructions. For an API or chatbot, the system message.

### How long should a system prompt be?

Long enough to cover the job, the audience, the rules and the format. For most assistants that's a few short paragraphs and some bullets.

### Is it free?

Yes. A free PromptItIn account writes the system prompt, no card needed.

## Related

- [ChatGPT Custom Instructions Generator](https://promptitin.com/free-tools/chatgpt-custom-instructions-generator)
- ["Act As" Role Prompt Generator](https://promptitin.com/free-tools/act-as-prompt-generator)
- [Prompt Framework Builder](https://promptitin.com/free-tools/prompt-framework-builder)