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System, User & Assistant Roles

Beginner

Every AI conversation is built from messages, and each message has a role. Understanding the three roles explains how to steer the model — and why some instructions stick while others don't.

The three roles​

  • System — top-level setup for the whole conversation: who the model should be, the rules, the format. Set once, applies throughout.
  • User — that's you: your questions and inputs, turn by turn.
  • Assistant — the model's replies. (You can also put words in the assistant's mouth as examples — see few-shot.)

Why the system prompt is your most powerful lever​

The system message frames everything that follows. It's where you set the model's role, standards, tone, and hard rules — and the model weights it heavily. If you want consistent behavior across a whole conversation (or app), put it here, not buried in a user turn.

In practice:

Same idea, three surfaces.

Practical tips​

  • Be specific in the system prompt about role, rules, and output format — it's the highest-leverage place to do it.
  • Keep user turns focused on the actual task; don't re-paste the rules every turn.
  • Conflicting instructions? A later, explicit user instruction can override a vague system one — be consistent to avoid surprises (Troubleshooting).

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