What problem does it solve? Measuring whether an LLM application actually works well is hard: manual spot-checks don't scale, regressions slip into production, and prompt or model changes lack objective validation. This Skill provides a complete evaluation toolkit covering automated metrics, human annotation, LLM-as-judge scoring, and statistical A/B testing. ## Core Features & Use Cases - Automated Metrics: Compute BLEU, ROUGE, BERTScore, perplexity, retrieval metrics (MRR, NDCG, Precision@K), and custom checks like groundedness, toxicity, and factuality. - LLM-as-Judge: Use Claude for pointwise quality ratings, pairwise response comparisons, and reference-based evaluation with structured Pydantic outputs. - Human Evaluation & A/B Testing: Build annotation forms, measure inter-rater agreement with Cohen's kappa, and run t-tests with Cohen's d effect sizes to detect statistically significant differences. - Regression Detection & Benchmarking: Compare new results against baselines with configurable thresholds and integrate with LangSmith for dataset-driven experiments. - Use Case: Before deploying a prompt change, run your test suite through the EvaluationSuite, compare variant scores with the ABTest analyzer, and block the release if the RegressionDetector flags a metric drop beyond your threshold. ## Quick Start Evaluate my LLM's answers on these test cases using accuracy, BERTScore, and an LLM judge, then tell me if the new prompt version is a statistically significant improvement over the baseline.