HOW LONG SHOULD A SYSTEM PROMPT BE?

There is no fixed number.

But every line must answer one question:

If this line were removed, would the Agent’s behavior change significantly?

If not, it can go.

An Instruction that is too long usually appears when you:

• stuff Knowledge into the Prompt;
• repeat Rules;
• over-explain;
• add a long list of edge cases to the core prompt.

Keep the Core Instruction compact.

Edge cases, methods, and detailed documents can be moved to Knowledge.