[How to define a custom evaluator | 🦜️🛠️ LangSmith](https://docs.smith.langchain.com/evaluation/how_to_guides/custom_evaluator): LLM should read this page when needing to create custom evaluators for LangSmith, understanding how to return different types of metrics, or implementing LLM-as-judge evaluators. The page explains how to define custom evaluator functions in LangSmith for both Python and TypeScript, including the required argument specifications, supported return types, and examples of different evaluation approaches such as exact matching, conciseness scoring, and using LLMs as judges.

