What Is LangChain Reference Docs?

Updated

LangChain Reference Docs (reference.langchain.com) is the unified API reference site for the LangChain ecosystem. It documents classes, functions, and types across LangChain, LangGraph, DeepAgents, LangSmith, and integrations, with packages browsable in Python, TypeScript, Java, and Go. Use it when you need to look up a specific API surface; use the separate main documentation site when you need guides, tutorials, or conceptual explanations.

What the site covers

The reference spans the whole ecosystem rather than a single library:

  • LangChain — core framework packages
  • LangGraph — graph-based agent and workflow APIs
  • DeepAgents — deep agent APIs
  • LangSmith — evaluation and observability APIs
  • Integrations — third-party model, store, and tool connectors

Each of these is documented at the level of classes, functions, and types, so the content is organized around code symbols rather than around tasks or narratives.

Reference docs vs. main documentation

The two sites serve different jobs, and the reference site states the split explicitly:

Need Where to go
Signature, parameters, return type of a class or function reference.langchain.com
Type definitions and package-level API browsing reference.langchain.com
Getting-started guides and tutorials Main documentation site
Conceptual explanations and how-to walkthroughs Main documentation site

A practical rule: if you already know the name of the symbol you want to call, the reference is the faster destination. If you know the outcome you want but not the API, start with the main docs and come back to the reference to confirm exact signatures.

Language and package coverage

The reference is not Python-only. It lists Python, TypeScript, Java, and Go packages, which matters if you are working in a polyglot stack or porting an implementation between SDKs. You browse by package, then drill into the classes, functions, and types that package exposes.

When it is worth using as your lookup entry point

It is a good primary entry point if:

  • You are already inside the LangChain ecosystem and need exact API details.
  • You want one place to check APIs across multiple ecosystem projects instead of jumping between separate sites.
  • You work across more than one language binding.

It is a weaker fit if you are evaluating whether to adopt LangChain at all, or if you need task-oriented instructions — those live on the main documentation site, not here.

Practical note

The site describes itself as API reference documentation. It does not present pricing or account requirements in the material available, so treat access and any login behavior as something to verify directly on the site rather than assuming it is unrestricted.