Quick answer: LLM observability — traces, evals, dataset management.
LangSmith is an LLM observability and monitoring platform built by LangChain, the creators of the popular LangChain framework for building applications with large language models. It provides comprehensive tracing, evaluation, and dataset management capabilities for LLM-powered applications. LangSmith captures detailed execution traces of LLM calls and chains, allowing developers to inspect exactly what's happening inside their AI systems. The platform enables performance evaluation through custom test cases and metrics, facilitates debugging of complex multi-step LLM workflows, and supports dataset curation for fine-tuning and experimentation. With its freemium pricing model, developers can start monitoring their applications at no cost, making it accessible for teams of any size building production LLM applications.