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Client-side evaluators run within your application, giving you real-time feedback during execution and full control over evaluation logic. You can use them via two main workflows:
WorkflowWhen to UseHow
Adding Metrics to TracesProduction monitoring, guardrailsenrich_span(), enrich_session()
Evaluator Functions for ExperimentsTesting against datasets, CI/CDDefine functions, pass to evaluate()

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Adding Metrics to Traces

Compute scores in your application code and attach them to traces for monitoring and analysis. Use cases: Format validation, safety checks, PII detection, latency tracking, relevance scores. 
import os
from honeyhive import HoneyHiveTracer, trace, enrich_span

HoneyHiveTracer.init(
    api_key=os.getenv("HH_API_KEY"),
    project=os.getenv("HH_PROJECT"),
)

@trace
def generate_response(query):
    response = call_llm(query)
    
    # Add metrics to this span
    enrich_span(metrics={
        "response_length": len(response),
        "contains_pii": check_pii(response),
        "relevance_score": compute_relevance(query, response),
    })
    
    return response
To see where to initialize the tracer for your environment, including AWS Lambda and long-running servers, see Tracer Initialization.
Metrics appear in the HoneyHive dashboard for charting, alerting, and filtering.
For complete documentation on adding metrics to traces, see Custom Metrics.

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Evaluator Functions for Experiments

Define scoring functions that run locally during evaluate() to score outputs against expected results.

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Writing an Evaluator

Evaluators receive three arguments and return a score: 
def my_evaluator(outputs, inputs, ground_truth):
    """
    Args:
        outputs: Return value from your function
        inputs: The inputs dict from the datapoint
        ground_truth: The ground_truth dict from the datapoint
    
    Returns:
        A score (number, boolean, or string)
    """
    expected = ground_truth.get("expected", "")
    return 1.0 if outputs == expected else 0.0

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Running Evaluators

Pass evaluator functions to evaluate(): 
import os
from honeyhive import evaluate

def accuracy(outputs, inputs, ground_truth):
    expected = ground_truth.get("intent", "")
    actual = outputs.get("intent", "")
    return 1.0 if expected == actual else 0.0

def my_classifier(datapoint):
    text = datapoint["inputs"]["text"]
    # Your classification logic
    return {"intent": classify(text)}

dataset = [
    {"inputs": {"text": "I need a refund"}, "ground_truth": {"intent": "billing"}},
    {"inputs": {"text": "App won't load"}, "ground_truth": {"intent": "technical"}},
]

result = evaluate(
    function=my_classifier,
    dataset=dataset,
    evaluators=[accuracy],
    api_key=os.getenv("HH_API_KEY"),
    project=os.getenv("HH_PROJECT"),
    name="intent-classifier-v1",
)
For a complete tutorial with real examples, see Run Your First Experiment.

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Evaluating Multi-Step Pipelines

For pipelines with multiple steps, combine both approaches:
  • Session-level: Pass evaluators to evaluate() for overall scoring
  • Span-level: Use enrich_span() within traced functions for step-specific metrics
import os
from honeyhive import evaluate
from honeyhive import trace, enrich_span

# Session-level evaluator
def answer_quality(outputs, inputs, ground_truth):
    expected = ground_truth.get("answer", "")
    return 1.0 if expected.lower() in outputs.lower() else 0.0

@trace
def retrieve_docs(query):
    docs = search_database(query)
    # Span-level metric
    enrich_span(metrics={"num_docs": len(docs), "retrieval_score": 0.85})
    return docs

@trace  
def generate_answer(docs, query):
    answer = call_llm(docs, query)
    enrich_span(metrics={"answer_length": len(answer)})
    return answer

def rag_pipeline(datapoint):
    query = datapoint["inputs"]["query"]
    docs = retrieve_docs(query)
    return generate_answer(docs, query)

result = evaluate(
    function=rag_pipeline,
    dataset=my_dataset,
    evaluators=[answer_quality],  # Scores the final output
    api_key=os.getenv("HH_API_KEY"),
    project=os.getenv("HH_PROJECT"),
    name="rag-eval",
)
After running, you’ll see both:
  • answer_quality scores at the session level
  • retrieval_score, num_docs, answer_length at the span level

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Next Steps

Custom Metrics

Full guide to adding metrics to traces

Run Your First Experiment

Complete tutorial with real examples

Server-Side Evaluators

Run evaluators on HoneyHive infrastructure

LLM-as-Judge

Use LLMs to evaluate outputs