System Prompt

A system prompt is a set of instructions given to an AI model before a conversation begins, typically invisible to the end user, that shapes how the model behaves throughout the interaction. System prompts define the model's persona, its constraints, its areas of focus, and its default behaviors. They're used to build AI products — a customer support chatbot has a system prompt that tells it to only answer questions about the company's products.

For organizations building custom AI tools, the system prompt is one of the most powerful levers for controlling output quality and consistency.