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n. / Prompts and context
System prompt
Definition
A system prompt is the standing set of instructions sent at the start of every call that tells the model its role, rules, tone and what tools it may use. The user does not see it.
In more detail
It is where you set boundaries, such as what to refuse and how to format answers. Because it is repeated on every step, it adds to input tokens and is a good candidate for prompt caching. It also is not a security boundary: a determined user can sometimes override or extract it, so enforce important rules in code as well.
Example
"You are a support agent for Acme. Only answer questions about orders. Use the lookup_order tool before quoting a status. Reply in two sentences."
Related terms
