How to return multiple scores in one evaluator

Sometimes it is useful for a custom evaluator or summary evaluator to return multiple metrics. For example, if you have multiple metrics being generated by an LLM judge, you can save time and money by making a single LLM call that generates multiple metrics instead of making multiple LLM calls. To return multiple scores using the Python SDK, simply return a list of dictionaries/objects of the following form:

[
    # 'key' is the metric name
    # 'score' is the value of a numerical metric
    {"key": string, "score": number},
    # 'value' is the value of a categorical metric
    {"key": string, "value": string},
    ... # You may log as many as you wish
]

To do so with the JS/TS SDK, return an object with a ‘results’ key and then a list of the above form

{results: [{ key: string, score: number }, ...]};

Each of these dictionaries can contain any or all of the feedback fields; check out the linked document for more information. Example:

Python: Requires langsmith>=0.2.0
TypeScript: Support for multiple scores is available in langsmith@0.1.32 and higher

def multiple_scores(outputs: dict, reference_outputs: dict) -> list[dict]:
    # Replace with real evaluation logic.
    precision = 0.8
    recall = 0.9
    f1 = 0.85
    return [
        {"key": "precision", "score": precision},
        {"key": "recall", "score": recall},
        {"key": "f1", "score": f1},
    ]