Free tool
System Prompt Builder
Generate a clean, professional system prompt from the proven Role · Context · Task · Format · Constraints framework. Works for ChatGPT, Claude, Gemini and open-source models.
Generated system prompt
Fill in the fields to build your prompt…
Based on the 5-part framework (Role · Context · Task · Format · Constraints) taught in our Prompt Engineering course.
What it is for
A system prompt sets the standing rules for every message in a conversation — who the model is, what it should always do, what it must never do. It is the difference between an assistant that behaves consistently and one that has to be re-instructed each time.
Getting it right matters more than getting any individual prompt right, because it applies to all of them.
How it works
The builder walks through the five components — role, context, task, format, constraints — and assembles them into a clean system prompt you can paste into ChatGPT, Claude, the API, or any tool that accepts one.
The structure is deliberately plain. Elaborate persona framing tends to produce elaborate output rather than better output; a clear statement of the job usually beats an imaginative one.
When to use it — and when not to
Use it when setting up a custom GPT or Claude Project, when defining the assistant behind a product feature, or when a team needs several people to get consistent results from the same tool.
For one-off questions a system prompt is overhead. If you are asking a model something once, just ask it.
Things worth knowing
Put the constraints last and make them explicit. Instructions near the end of a prompt carry more weight in practice, and negative instructions — do not speculate, do not use marketing language, say so when the answer is not in the provided material — are where most of the reliability comes from.
Test the system prompt against your worst case, not your typical one. It is easy to write rules that work on a well-formed request; the value is in what happens when the input is vague or hostile.
Frequently asked questions
What makes a good system prompt?
A strong system prompt defines five things: the role the AI should adopt, the context it needs, the specific task, the output format, and hard constraints. Missing any of these is the most common cause of vague AI output.
Does this work for Claude and Gemini too?
Yes. The five-part framework is model-agnostic and works across ChatGPT, Claude, Gemini, Grok and open-source models. Claude tends to follow long nuanced instructions particularly well.