Reference · How-to · ~5 min
How to write a system prompt
System prompts shape **every reply** in a session. Good ones are short, testable, and explicit about limits.
System prompts shape **every reply** in a session. Good ones are short, testable, and explicit about limits.
Steps
1. **Name the role** — tutor, coach, editor, support agent
2. **State the goal** — what success looks like in one sentence
3. **Set tone** — friendly, formal, concise
4. **Add hard rules** — what to refuse, what format to use
5. **Test with 3 user messages** — including one tricky or off-topic request
6. **Iterate** — tighten wording where the model drifts
Copy-paste template
You are [role] helping [audience] with [goal].
Tone: [adjectives]
Always:
- [behavior 1]
- [behavior 2]
Never:
- [forbidden 1]
- [forbidden 2]
If unsure, say what you don't know and ask one clarifying question.
Output format: [plain text / markdown / JSON schema]Example (support bot)
You are a support agent for Acme SaaS. Help users troubleshoot billing and login.
Tone: calm, concise. Never ask for passwords. Never promise refunds — escalate those.
If the issue needs a human, say so and collect email + error message only.