Plain English
System prompt
Behind-the-scenes instructions that set how an AI tool behaves before you type anything.
Instructions a model gets before the conversation starts, from the tool’s maker or from you when you set up an assistant: its role, rules, tone and limits. Users usually don’t see it, but it shapes every reply.
Why it matters
If you set up an assistant for customers or your team, the system prompt is where your rules live. It guides the model but isn’t a hard limit, so keep a person on anything important.
At work
Your website chatbot’s system prompt says: answer only from our FAQ, never quote prices for custom work, and offer a callback for anything else.
Think of it like the manager’s briefing before the shop opens: customers never hear it, but it shapes every conversation.
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