Three ways to steer a model before it answers — set the rules with a system prompt, give it a persona with a role, and feed it background with context. Learn when each one is the right lever.
Why: the system prompt sets standing rules that apply to every turn — format, safety limits, what the model must never do. Where: it goes in the System box, separate from the user message, so users cannot easily override it. When: use it for constraints you want enforced for the whole conversation.
[System]
You are a support assistant for a banking app.
Rules:
- Never ask for or repeat full card numbers or passwords.
- If a request is outside banking, politely decline.
- Always answer in under 80 words.
[User]
How do I reset my PIN?Why: a role primes the vocabulary, depth, and viewpoint of the answer — "explain like a tax lawyer" reads very differently from "explain like a friend". When: use it to control tone and expertise level. Where: it can live in the system prompt or the first line of the user prompt.
You are a patient ski instructor talking to a nervous first-timer.
Explain how to slow down and stop on a gentle slope.
Use short steps and reassuring language.Why: context is the facts the model could not know — your data, the current date, the document to summarise. When: use it whenever the right answer depends on information specific to your situation. Where: clearly fenced off from the instruction so the model treats it as reference, not commands.
Use ONLY the policy below to answer. If the answer is not in
the policy, say "Not covered in policy."
[Policy]
Refunds are available within 30 days of purchase with a receipt.
Digital goods are non-refundable once downloaded.
[Question]
Can I refund an e-book I downloaded yesterday?Why: real prompts stack the levers — rules from the system, a persona for tone, and context for facts. When: layer them once a single technique is not enough. Where: keep each in its own labelled block so you can tweak one without breaking the others.
[System]
You answer strictly from the provided context. Under 100 words.
[Role]
You are a friendly onboarding specialist.
[Context]
The free plan allows 3 projects. Paid plans start at $9/month
for unlimited projects.
[User]
I have 4 projects I want to manage — what are my options?