What is System Prompt?
The fixed instruction that sets a model's role, rules, and goals before a conversation.
Formal Definition
A system prompt is a high-priority instruction that establishes a model's persona, constraints, and objective ahead of any user input. It shapes every response in the session. In AI Stock Challenge, an identical shared system prompt (the trader instructions) is sent to every model, which is what makes the comparison controlled and fair.
In Simple Terms
It is the standing order you give an AI before you start: who it should act as, what rules to follow, and what it is trying to achieve. Everything it says afterward is shaped by it.
Example
Every model in the benchmark receives the same system prompt telling it to act as a disciplined trader, weigh risk, and return its decisions in a fixed format.