The officially maintained MCP Python SDK for building servers and clients, not itself a fixed-capability server; documentation, a migration guide, and community support channels are all present, with v2 as the current stable line and v1.x still receiving security patches.
This is the official Python implementation of the Model Context Protocol (MCP), maintained by the modelcontextprotocol organization. It is not a standalone server with a fixed set of tools, but a development library: it lets developers write MCP servers that expose tools, resources, and prompts, or clients that connect to any MCP server. The SDK supports all three standard transports (stdio, Streamable HTTP, and SSE) and derives JSON Schema automatically from Python type hints, eliminating hand-written protocol parsing. It is currently on the v2 major line (supporting the 2026-07-28 spec revision and all earlier ones), while v1.x continues to receive critical bug fixes and security patches on its own branch. Requires Python 3.10+.
Install with uv add "mcp[cli]" or pip install "mcp[cli]" (the cli extra adds the mcp dev/mcp run/mcp install command-line tool; install plain mcp if the CLI isn't needed). Because pip install mcp now installs 2.x by default, projects still relying on v1 behavior should pin an upper bound such as mcp>=1.28,<2 until migrated. After installing, write a server script using @mcp.tool() and @mcp.resource() decorators and run it with uv run mcp dev server.py to debug it in the MCP Inspector.