functions = [
    {
        "name": "extract_document_metadata",
        "parameters": {
            "type": "object",
            "properties": {
                "methodology_type": {
                    "type": "string",
                    "enum": ["experimental", "observational", "review", "simulation", "mixed"]
                },
                "dataset_source": {"type": "string"},
                "primary_metric": {"type": "string"},
                "year": {"type": "integer"},
                "confidence_score": {"type": "number", "minimum": 0, "maximum": 1}
            },
            "required": ["methodology_type", "dataset_source", "year"]
        }
    }
]

response = openai_client.chat.completions.create(
    model="gpt-4-turbo",
    messages=messages,
    functions=functions,
    function_call={"name": "extract_document_metadata"},
    temperature=0
)