What problem does it solve? Measuring whether an LLM application actually works well is hard: single metrics mislead, regressions slip into production, and prompt changes lack statistical validation. This Skill provides a systematic evaluation framework covering automated metrics, human evaluation, LLM-as-judge, and A/B testing. ## Core Features & Use Cases - Automated Metrics: Compute BLEU, ROUGE, BERTScore, perplexity, classification metrics, and RAG retrieval metrics like MRR and NDCG. - LLM-as-Judge & Human Evaluation: Score outputs with pointwise or pairwise LLM judges, and structure human annotation with inter-rater agreement via Cohen's kappa. - A/B Testing & Regression Detection: Run t-tests with Cohen's d effect sizes and detect metric regressions against baselines before deployment. - Use Case: Before shipping a prompt change, run your test suite through the evaluation harness, compare variants with statistical tests, and block deployment if any metric regresses beyond your threshold. ## Quick Start Ask the AI to evaluate your model's responses against a set of test cases using BLEU, BERTScore, and an LLM judge, then report which prompt variant performs better.