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What is System prompt?

Updated July 21, 2026 · by Pedro

A system prompt is the persistent instruction layer that sets rules for a session. Product tools like tknctrl generate user-facing prompts you paste into Cursor, Claude, or ChatGPT.

Why does this term matter for AI prompts?

Precise vocabulary reduces vague instructions. When you name system prompt correctly in a brief, Claude, Cursor, and GPT spend fewer tokens guessing. Pair definitions with structure on AI prompt builder and cost math on prompt token cost.

More glossary terms

Full list: prompt engineering glossary.

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