LLM-as-a-Judge: What It Is, Why It Works, and How to Use It to Evaluate AI Models

Large Language Models can be used as expert evaluators to judge the performance of other AI systems, a paradigm known as "LLM-as-a-Judge." This technique is especially powerful for complex problems where large, labeled datasets are unavailable, providing rapid feedback without months of manual data collection. By acting as a judge, the LLM can assess a model's outputs, help build a high-quality training set for improvement, and monitor performance over time. To ensure reliability in a production setting, it's crucial to provide the LLM with a clear persona, few-shot examples, and prompts that encourage step-by-step reasoning before it delivers a final verdict.