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103 lines
3.7 KiB
Markdown
103 lines
3.7 KiB
Markdown
# MCP Python SDK
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!!! info "You are viewing the in-development v2 documentation"
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For the current stable release, see the [v1.x documentation](https://py.sdk.modelcontextprotocol.io/).
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New to v2, or coming from v1? **[What's new in v2](whats-new.md)** is the five-minute tour of what changed.
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Trying v2? [Tell us what you find](https://github.com/modelcontextprotocol/python-sdk/issues/new?template=v2-feedback.yaml) — it is the most useful thing you can do for the SDK right now.
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The **Model Context Protocol (MCP)** lets applications provide context to LLMs in a standardized way, separating the concern of *providing* context from the LLM interaction itself.
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This is the official Python SDK for it. With it you can:
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* **Build MCP servers** that expose tools, resources, and prompts to any MCP host.
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* **Build MCP clients** that connect to any MCP server.
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* Speak every standard transport: stdio, Streamable HTTP, and SSE.
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## Requirements
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Python 3.10+.
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## Installation
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=== "uv"
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```bash
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uv add "mcp[cli]==2.0.0b1"
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```
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=== "pip"
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```bash
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pip install "mcp[cli]==2.0.0b1"
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```
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The `[cli]` extra gives you the `mcp` command; you'll want it for development.
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!!! warning "Pin the version while v2 is in beta"
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Installers never select a pre-release unless you name one, so an unpinned `uv add "mcp[cli]"`
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gives you the latest **v1.x** release, which this documentation does not describe. Check
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[PyPI](https://pypi.org/project/mcp/#history) for the newest beta before you copy the line
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above. See [Installation](get-started/installation.md) for the details.
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## Example
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### Create it
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Create a file `server.py`:
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```python title="server.py"
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--8<-- "docs_src/index/tutorial001.py"
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```
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That's a complete MCP server.
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It exposes one **tool**, `add`, and one templated **resource**, `greeting://{name}`.
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### Run it
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```console
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uv run mcp dev server.py
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```
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This starts your server and opens the [MCP Inspector](https://github.com/modelcontextprotocol/inspector), an interactive UI for poking at it. Open the URL it prints.
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!!! note
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The Inspector is a Node.js app, so `mcp dev` needs `npx` on your `PATH`.
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### Try it
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In the Inspector, go to **Tools** and call `add` with `a=1`, `b=2`.
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You get `3` back. ✨
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The Inspector built that form (a required integer field for `a`, another for `b`) from your type hints. So will Claude, and every other MCP host.
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Now go to **Resources** and read `greeting://World`:
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```text
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Hello, World!
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```
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### Recap
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Look again at what you did **not** write:
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* No JSON Schema. `a: int, b: int` *is* the schema.
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* No request parsing, no serialization, no validation code.
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* No protocol handling at all.
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You wrote two Python functions with type hints and a docstring. The SDK does the rest.
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## Where to go next
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* **[Get started](get-started/index.md)** takes you from install to a working, tested server.
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* Building an application that *uses* MCP servers? Start with **[Clients](client/index.md)**.
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* Already have a FastAPI or Starlette app? **[Add to an existing app](run/asgi.md)** mounts an MCP server inside it.
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* Hunting an exact error message? **[Troubleshooting](troubleshooting.md)** is keyed by the verbatim text.
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* Wondering what changed in v2? **[What's new in v2](whats-new.md)** is the five-minute tour.
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* Migrating from v1? Start with the **[Migration Guide](migration.md)**.
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* Hunting for an exact signature? The **[API Reference](api/mcp/index.md)** is generated from the source.
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* Reading with an LLM? This documentation is also published in the [llms.txt](https://llmstxt.org/) format:
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[llms.txt](https://py.sdk.modelcontextprotocol.io/v2/llms.txt) is an index of the pages, and
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[llms-full.txt](https://py.sdk.modelcontextprotocol.io/v2/llms-full.txt) contains every page in a single file.
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