What is System prompt?
Updated May 2026
A system prompt is the instructions you give an AI before any conversation starts, telling it who it is and how to behave.
Every modern AI agent has a system prompt. It's where you tell the model 'you are a coaching assistant for Priya, speak in her voice, never quote a price you don't have a template for, end politely on chitchat.'
Good system prompts are specific, voice-led, and bounded. Generic system prompts produce generic AI tone — exactly what kills voice fidelity for creators.
Frequently asked questions
How long should a system prompt be?
As long as needed, as short as possible. 200-800 words is typical for a focused agent. Much longer than that and the model starts ignoring later instructions.
Related terms
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