Practical MCP with FastMCP & LangChain

What Changed With FastMCP?

After the initial release, MCP evolved. The ecosystem grew. Use cases expanded. FastMCP also evolved independently. FastMCP 2.0 (and now FastMCP 3.x) is no longer just a lightweight decorator-based helper. It became a productivity layer with a more modular architecture. It now includes:

• A composition framework.
• A proxy layer for other MCP servers.
• A client + server infrastructure toolkit.
• A higher-level orchestration system.
• A way to generate MCP servers from OpenAPI and FastAPI.

The scope diverged significantly from the simple helper included in the official SDK. Because of that divergence, there is now potential confusion:

• The SDK still contains a FastMCP