System Prompt
A high-priority instruction that sets the role, behavior, constraints, and goals for an AI model within an application.
A system prompt is the instruction layer that tells a model how it should behave before user messages are considered. It often defines the assistant's role, tone, rules, priorities, formatting, and safety constraints.
In practice, the system prompt is one of the most important controls available to product teams. It shapes how the model responds across every interaction in the app and helps make the assistant consistent and useful.
What System Prompts Commonly Specify
- Role — teacher, support agent, coding assistant, analyst
- Tone — concise, friendly, formal, technical
- Boundaries — what the model should or should not do
- Output style — markdown, JSON, bullets, short answers, citations
A strong system prompt does not guarantee perfect behavior, but it greatly improves consistency. It is often combined with examples, tool schemas, and guardrails to create robust AI product experiences.