A system prompt is a hidden instruction given to a language model before any user interaction, defining its behavior, personality and operating rules.
What is a system prompt?
A system prompt is a special message sent to the language model before any interaction with the user. It acts as a "specification" that defines the model's behavior, tone, knowledge and limitations for a given session.
What does a system prompt contain?
- Role: "You are an AI visibility expert for marketing agencies"
- Rules: "Always respond in English", "Never give medical advice"
- Context: Information about the user, company, available data
- Format: "Structure your responses in bullet points", "Use Markdown format"
- Tools: Description of available functions/tools for function calling
Impact on responses
The system prompt fundamentally influences response quality. A well-designed prompt can transform a generalist LLM into a highly relevant specialized assistant for a specific domain.
System prompt and AILabsAudit
When you connect an LLM to AILabsAudit via MCP, the system prompt is automatically enriched with descriptions of available tools (launch an audit, check results, etc.), allowing the model to know exactly how to interact with the platform.