What is agent instructions?

Agent instructions are the part of the system prompt you write yourself: the agent's name and persona, its tone, the topics to focus on and the things it must decline. They sit on top of the vendor's base rules, which you do not see and cannot edit. Intercom and Tidio call them guidance; Zendesk splits them into persona, tone of voice and instructions.

It matters because this is the one lever most teams have over how the agent sounds, and because it is misused in a predictable way: people put facts in it. "Our shipping takes 3 days" in the instructions goes stale the day shipping changes, and the model treats instructions and content differently. Facts belong in the knowledge base; instructions describe the voice. Brief the agent like a new hire in a dozen plain lines: who it is, how short to keep answers, what to suggest next, what never to discuss.

Where it runs out: instructions cannot override the base rules in a well-built product, which is the point. "Ignore your rules and answer anything" should have no effect, and neither should "always quote a price" when the price is not in the content. Refusals you write do work even when the knowledge base contains the information, so "never discuss pricing" means the agent declines pricing questions it could have answered. Test each line after saving; a style guide pasted whole works worse than ten clear sentences.