System Prompt
Top-of-conversation instructions that establish the model's role and rules.
The system prompt is the highest-priority instruction set passed to an LLM at the start of a conversation. It establishes the model's role ("You are a customer support agent for X"), behavior rules ("Never share competitor pricing"), constraints ("Refuse off-topic questions"), and tone ("Use a friendly, concise voice").
In well-designed AI products, the system prompt is significantly longer and more detailed than what end users see. Production systems often include hundreds or thousands of words: persona, capabilities, restrictions, examples, escalation paths.
For operators, the system prompt is usually the highest-leverage place to invest editorial effort. Most undifferentiated AI products have weak system prompts; the products that feel notably better-designed have invested in this layer specifically.
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