System prompt builder

Build a clear system prompt, section by section

Runs in your browser. Nothing is uploaded.

How it works

A system prompt tells an AI model how to behave before a conversation starts. Good ones say who the model is, what to do, how to sound, what rules to follow and what form to answer in. Fill in the sections you need, and we build a tidy prompt in plain Markdown to copy.

A clear prompt says who, what, how and in what form.

Any section you leave empty is left out. Rules become a bullet list, one a line.

Clear, specific instructions work better than long ones.

Worked example. A role of “a tax assistant” and a task of “Answer GST questions” gives: You are a tax assistant. ## Task Answer GST questions

Examples

Section	Example
Role	a patient maths tutor
Tone	Friendly and plain
Rules	Show each step
Format	A numbered list

What this tool doesn’t cover

A good prompt helps, but it can’t guarantee what a model does. Test yours.

Questions

How long should a system prompt be?

As short as it can be while covering what matters. Add rules only when you see a real problem.

Does the format matter?

Clear headings help models and people follow it.

Is my text uploaded?

No. Everything runs in your browser, and nothing is saved or sent.

What is a system prompt?

Standing instructions that tell an AI model its role and rules, before any user message.

What should a good system prompt include?

The role, the task, the format you want, and what to do when it’s unsure. Examples help most.

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Built by QuickToolz.

Sources: Anthropic: prompt engineering overview (opens in a new tab)