The system prompt that defines the LLM application's intended behavior, role, and operational scope. The system prompt provides critical context about the application's purpose and constraints, such as "You are a customer support assistant for an e-commerce platform" or "This application provides medical information for healthcare professionals." This information helps the Firewall for AI understand the legitimate use case boundaries and detect prompts that attempt to override or bypass the intended system behavior through prompt injection attacks. Maximum length is 2048 characters. This field is optional but recommended for improved security posture.