What is it?
A system prompt is a set of instructions sent by an application to guide the model's behavior.
It can define a role, rules, boundaries, tone, or output format. It guides a response at runtime but does not retrain the model.
04 · Prompting & System Design · Topic 01
What is a System Prompt?
A system prompt is a set of instructions that guides an AI model inside an application.
Think of it like...
Think of it like a workplace handbook.
The handbook sets rules before a customer arrives. A system prompt gives an AI application guidance before it handles the current request. The model is not a person, and the rules do not guarantee every response.
How it works
1 · Add rulesSet behaviorThe application prepares system instructions.
2 · Add requestReceive the user promptThe current task enters the input.
3 · Add contextSupply informationRelevant documents or tool results may be included.
4 · GenerateRun the modelThe model uses the combined input.
5 · ReviewCheck the outputImportant results may need validation.
Real-world examples
Everyday example · Support
Input: a customer asks about a refund
AI / System: follows the company policy and avoids inventing rules
Output: a policy-based answer or human review
Business example · Invoice data
Input: an invoice and a required schema
AI / System: extracts fields and marks uncertain values
Output: structured invoice data
What it is NOT
System Prompt ≠ User Prompt
System prompt: application-level guidance.
User prompt: the request for the current turn.
System Prompt ≠ Model Training
System prompt: runtime instructions.
Model training: changes learned parameters.
System Prompt ≠ Guaranteed Control
System prompt: guides likely behavior.
Guaranteed control: certainty that every output follows every rule.
Related concepts
Application → System Prompt + User Prompt + Context → LLM → Output
Explore next
Remember this
A system prompt guides an AI application's behavior at runtime; it does not guarantee the output.
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