'AI_COMPLETE Structured OutputS (and its predecessor 'COMPLETE Structured Outputs') specifically allows supplying a JSON schema as the 'response_format' argument to ensure completion responses follow a predefined structure. This significantly reduces the need for post-processing and enables seamless integration with systems requiring deterministic responses. The JSON schema object defines the structure, data types, and constraints, including required fields. While prompting the model to 'Respond in JSON' can improve accuracy for complex tasks, the 'response_format' argument is the direct mechanism for enforcing the schema. Option A is a form of prompt engineering, which can help but does not guarantee strict adherence as 'response_format' does. Option B controls randomness and length, not output structure. Option D is less efficient for extracting multiple related fields compared to a single structured output call. Option E's 'guardrails' are for filtering unsafe or harmful content, not for enforcing output format.