chore: add D212 lint rule to enforce Google-style docstrings (#1892)

README.md

@@ -136,8 +136,7 @@ Let's create a simple MCP server that exposes a calculator tool and some data:
 
 <!-- snippet-source examples/snippets/servers/fastmcp_quickstart.py -->
 ```python
-"""
+"""FastMCP quickstart example.
-FastMCP quickstart example.
 
 Run from the repository root:
     uv run examples/snippets/servers/fastmcp_quickstart.py
@@ -727,8 +726,7 @@ Client usage:
 
 <!-- snippet-source examples/snippets/clients/completion_client.py -->
 ```python
-"""
+"""cd to the `examples/snippets` directory and run:
-cd to the `examples/snippets` directory and run:
 uv run completion-client
 """
 
@@ -1004,8 +1002,7 @@ MCP servers can use authentication by providing an implementation of the `TokenV
 
 <!-- snippet-source examples/snippets/servers/oauth_server.py -->
 ```python
-"""
+"""Run from the repository root:
-Run from the repository root:
 uv run examples/snippets/servers/oauth_server.py
 """
 
@@ -1245,8 +1242,7 @@ Note that `uv run mcp run` or `uv run mcp dev` only supports server using FastMC
 
 <!-- snippet-source examples/snippets/servers/streamable_config.py -->
 ```python
-"""
+"""Run from the repository root:
-Run from the repository root:
 uv run examples/snippets/servers/streamable_config.py
 """
 
@@ -1283,8 +1279,7 @@ You can mount multiple FastMCP servers in a Starlette application:
 
 <!-- snippet-source examples/snippets/servers/streamable_starlette_mount.py -->
 ```python
-"""
+"""Run from the repository root:
-Run from the repository root:
 uvicorn examples.snippets.servers.streamable_starlette_mount:app --reload
 """
 
@@ -1394,8 +1389,7 @@ You can mount the StreamableHTTP server to an existing ASGI server using the `st
 
 <!-- snippet-source examples/snippets/servers/streamable_http_basic_mounting.py -->
 ```python
-"""
+"""Basic example showing how to mount StreamableHTTP server in Starlette.
-Basic example showing how to mount StreamableHTTP server in Starlette.
 
 Run from the repository root:
     uvicorn examples.snippets.servers.streamable_http_basic_mounting:app --reload
@@ -1442,8 +1436,7 @@ _Full example: [examples/snippets/servers/streamable_http_basic_mounting.py](htt
 
 <!-- snippet-source examples/snippets/servers/streamable_http_host_mounting.py -->
 ```python
-"""
+"""Example showing how to mount StreamableHTTP server using Host-based routing.
-Example showing how to mount StreamableHTTP server using Host-based routing.
 
 Run from the repository root:
     uvicorn examples.snippets.servers.streamable_http_host_mounting:app --reload
@@ -1490,8 +1483,7 @@ _Full example: [examples/snippets/servers/streamable_http_host_mounting.py](http
 
 <!-- snippet-source examples/snippets/servers/streamable_http_multiple_servers.py -->
 ```python
-"""
+"""Example showing how to mount multiple StreamableHTTP servers with path configuration.
-Example showing how to mount multiple StreamableHTTP servers with path configuration.
 
 Run from the repository root:
     uvicorn examples.snippets.servers.streamable_http_multiple_servers:app --reload
@@ -1548,8 +1540,7 @@ _Full example: [examples/snippets/servers/streamable_http_multiple_servers.py](h
 
 <!-- snippet-source examples/snippets/servers/streamable_http_path_config.py -->
 ```python
-"""
+"""Example showing path configuration when mounting FastMCP.
-Example showing path configuration when mounting FastMCP.
 
 Run from the repository root:
     uvicorn examples.snippets.servers.streamable_http_path_config:app --reload
@@ -1644,8 +1635,7 @@ For more control, you can use the low-level server implementation directly. This
 
 <!-- snippet-source examples/snippets/servers/lowlevel/lifespan.py -->
 ```python
-"""
+"""Run from the repository root:
-Run from the repository root:
 uv run examples/snippets/servers/lowlevel/lifespan.py
 """
 
@@ -1761,8 +1751,7 @@ The lifespan API provides:
 
 <!-- snippet-source examples/snippets/servers/lowlevel/basic.py -->
 ```python
-"""
+"""Run from the repository root:
-Run from the repository root:
 uv run examples/snippets/servers/lowlevel/basic.py
 """
 
@@ -1840,8 +1829,7 @@ The low-level server supports structured output for tools, allowing you to retur
 
 <!-- snippet-source examples/snippets/servers/lowlevel/structured_output.py -->
 ```python
-"""
+"""Run from the repository root:
-Run from the repository root:
 uv run examples/snippets/servers/lowlevel/structured_output.py
 """
 
@@ -1943,8 +1931,7 @@ For full control over the response including the `_meta` field (for passing data
 
 <!-- snippet-source examples/snippets/servers/lowlevel/direct_call_tool_result.py -->
 ```python
-"""
+"""Run from the repository root:
-Run from the repository root:
 uv run examples/snippets/servers/lowlevel/direct_call_tool_result.py
 """
 
@@ -2023,9 +2010,7 @@ For servers that need to handle large datasets, the low-level server provides pa
 
 <!-- snippet-source examples/snippets/servers/pagination_example.py -->
 ```python
-"""
+"""Example of implementing pagination with MCP server decorators."""
-Example of implementing pagination with MCP server decorators.
-"""
 
 import mcp.types as types
 from mcp.server.lowlevel import Server
@@ -2068,9 +2053,7 @@ _Full example: [examples/snippets/servers/pagination_example.py](https://github.
 
 <!-- snippet-source examples/snippets/clients/pagination_client.py -->
 ```python
-"""
+"""Example of consuming paginated MCP endpoints from a client."""
-Example of consuming paginated MCP endpoints from a client.
-"""
 
 import asyncio
 
@@ -2129,8 +2112,7 @@ The SDK provides a high-level client interface for connecting to MCP servers usi
 
 <!-- snippet-source examples/snippets/clients/stdio_client.py -->
 ```python
-"""
+"""cd to the `examples/snippets/clients` directory and run:
-cd to the `examples/snippets/clients` directory and run:
 uv run client
 """
 
@@ -2221,8 +2203,7 @@ Clients can also connect using [Streamable HTTP transport](https://modelcontextp
 
 <!-- snippet-source examples/snippets/clients/streamable_basic.py -->
 ```python
-"""
+"""Run from the repository root:
-Run from the repository root:
 uv run examples/snippets/clients/streamable_basic.py
 """
 
@@ -2261,8 +2242,7 @@ When building MCP clients, the SDK provides utilities to help display human-read
 
 <!-- snippet-source examples/snippets/clients/display_utilities.py -->
 ```python
-"""
+"""cd to the `examples/snippets` directory and run:
-cd to the `examples/snippets` directory and run:
 uv run display-utilities-client
 """
 
@@ -2346,8 +2326,7 @@ The SDK includes [authorization support](https://modelcontextprotocol.io/specifi
 
 <!-- snippet-source examples/snippets/clients/oauth_client.py -->
 ```python
-"""
+"""Before running, specify running MCP RS server URL.
-Before running, specify running MCP RS server URL.
 To spin up RS server locally, see
     examples/servers/simple-auth/README.md
 

examples/clients/conformance-auth-client/mcp_conformance_auth_client/__init__.py

@@ -1,6 +1,5 @@
 #!/usr/bin/env python3
-"""
+"""MCP OAuth conformance test client.
-MCP OAuth conformance test client.
 
 This client is designed to work with the MCP conformance test framework.
 It automatically handles OAuth flows without user interaction by programmatically
@@ -89,8 +88,7 @@ class InMemoryTokenStorage(TokenStorage):
 
 
 class ConformanceOAuthCallbackHandler:
-    """
+    """OAuth callback handler that automatically fetches the authorization URL
-    OAuth callback handler that automatically fetches the authorization URL
     and extracts the auth code, without requiring user interaction.
 
     This mimics the behavior of the TypeScript ConformanceOAuthProvider.
@@ -101,8 +99,7 @@ class ConformanceOAuthCallbackHandler:
         self._state: str | None = None
 
     async def handle_redirect(self, authorization_url: str) -> None:
-        """
+        """Fetch the authorization URL and extract the auth code from the redirect.
-        Fetch the authorization URL and extract the auth code from the redirect.
 
         The conformance test server returns a redirect with the auth code,
         so we can capture it programmatically.
@@ -148,8 +145,7 @@ class ConformanceOAuthCallbackHandler:
 
 
 async def run_authorization_code_client(server_url: str) -> None:
-    """
+    """Run the conformance test client with authorization code flow.
-    Run the conformance test client with authorization code flow.
 
     This function:
     1. Connects to the MCP server with OAuth authorization code flow
@@ -180,8 +176,7 @@ async def run_authorization_code_client(server_url: str) -> None:
 
 
 async def run_client_credentials_jwt_client(server_url: str) -> None:
-    """
+    """Run the conformance test client with client credentials flow using private_key_jwt (SEP-1046).
-    Run the conformance test client with client credentials flow using private_key_jwt (SEP-1046).
 
     This function:
     1. Connects to the MCP server with OAuth client_credentials grant
@@ -223,8 +218,7 @@ async def run_client_credentials_jwt_client(server_url: str) -> None:
 
 
 async def run_client_credentials_basic_client(server_url: str) -> None:
-    """
+    """Run the conformance test client with client credentials flow using client_secret_basic.
-    Run the conformance test client with client credentials flow using client_secret_basic.
 
     This function:
     1. Connects to the MCP server with OAuth client_credentials grant

examples/clients/simple-auth-client/mcp_simple_auth_client/main.py

@@ -1,6 +1,5 @@
 #!/usr/bin/env python3
-"""
+"""Simple MCP client example with OAuth authentication support.
-Simple MCP client example with OAuth authentication support.
 
 This client connects to an MCP server using streamable HTTP transport with OAuth.
 

examples/clients/sse-polling-client/mcp_sse_polling_client/main.py

@@ -1,5 +1,4 @@
-"""
+"""SSE Polling Demo Client
-SSE Polling Demo Client
 
 Demonstrates the client-side auto-reconnect for SSE polling pattern.
 

examples/fastmcp/complex_inputs.py

@@ -1,5 +1,4 @@
-"""
+"""FastMCP Complex inputs Example
-FastMCP Complex inputs Example
 
 Demonstrates validation via pydantic with complex models.
 """

examples/fastmcp/desktop.py

@@ -1,5 +1,4 @@
-"""
+"""FastMCP Desktop Example
-FastMCP Desktop Example
 
 A simple example that exposes the desktop directory as a resource.
 """

examples/fastmcp/direct_call_tool_result_return.py

@@ -1,6 +1,4 @@
-"""
+"""FastMCP Echo Server with direct CallToolResult return"""
-FastMCP Echo Server with direct CallToolResult return
-"""
 
 from typing import Annotated
 

examples/fastmcp/echo.py

@@ -1,6 +1,4 @@
-"""
+"""FastMCP Echo Server"""
-FastMCP Echo Server
-"""
 
 from mcp.server.fastmcp import FastMCP
 

examples/fastmcp/icons_demo.py

@@ -1,5 +1,4 @@
-"""
+"""FastMCP Icons Demo Server
-FastMCP Icons Demo Server
 
 Demonstrates using icons with tools, resources, prompts, and implementation.
 """

examples/fastmcp/logging_and_progress.py

@@ -1,6 +1,4 @@
-"""
+"""FastMCP Echo Server that sends log messages and progress updates to the client"""
-FastMCP Echo Server that sends log messages and progress updates to the client
-"""
 
 import asyncio
 

examples/fastmcp/memory.py

@@ -4,8 +4,7 @@
 
 # uv pip install 'pydantic-ai-slim[openai]' asyncpg numpy pgvector
 
-"""
+"""Recursive memory system inspired by the human brain's clustering of memories.
-Recursive memory system inspired by the human brain's clustering of memories.
 Uses OpenAI's 'text-embedding-3-small' model and pgvector for efficient
 similarity search.
 """

examples/fastmcp/parameter_descriptions.py

@@ -1,6 +1,4 @@
-"""
+"""FastMCP Example showing parameter descriptions"""
-FastMCP Example showing parameter descriptions
-"""
 
 from pydantic import Field
 

examples/fastmcp/screenshot.py

@@ -1,5 +1,4 @@
-"""
+"""FastMCP Screenshot Example
-FastMCP Screenshot Example
 
 Give Claude a tool to capture and view screenshots.
 """
@@ -15,8 +14,7 @@ mcp = FastMCP("Screenshot Demo")
 
 @mcp.tool()
 def take_screenshot() -> Image:
-    """
+    """Take a screenshot of the user's screen and return it as an image. Use
-    Take a screenshot of the user's screen and return it as an image. Use
     this tool anytime the user wants you to look at something they're doing.
     """
     import pyautogui

examples/fastmcp/simple_echo.py

@@ -1,6 +1,4 @@
-"""
+"""FastMCP Echo Server"""
-FastMCP Echo Server
-"""
 
 from mcp.server.fastmcp import FastMCP
 

examples/fastmcp/text_me.py

@@ -2,8 +2,7 @@
 # dependencies = []
 # ///
 
-"""
+"""FastMCP Text Me Server
-FastMCP Text Me Server
 --------------------------------
 This defines a simple FastMCP server that sends a text message to a phone number via https://surgemsg.com/.
 

examples/fastmcp/unicode_example.py

@@ -1,5 +1,4 @@
-"""
+"""Example FastMCP server that uses Unicode characters in various places to help test
-Example FastMCP server that uses Unicode characters in various places to help test
 Unicode handling in tools and inspectors.
 """
 
@@ -10,8 +9,7 @@ mcp = FastMCP()
 
 @mcp.tool(description="🌟 A tool that uses various Unicode characters in its description: á é í ó ú ñ 漢字 🎉")
 def hello_unicode(name: str = "世界", greeting: str = "¡Hola") -> str:
-    """
+    """A simple tool that demonstrates Unicode handling in:
-    A simple tool that demonstrates Unicode handling in:
     - Tool description (emojis, accents, CJK characters)
     - Parameter defaults (CJK characters)
     - Return values (Spanish punctuation, emojis)

examples/fastmcp/weather_structured.py

@@ -1,5 +1,4 @@
-"""
+"""FastMCP Weather Example with Structured Output
-FastMCP Weather Example with Structured Output
 
 Demonstrates how to use structured output with tools to return
 well-typed, validated data that clients can easily process.

examples/servers/everything-server/mcp_everything_server/server.py

@@ -1,6 +1,5 @@
 #!/usr/bin/env python3
-"""
+"""MCP Everything Server - Conformance Test Server
-MCP Everything Server - Conformance Test Server
 
 Server implementing all MCP features for conformance testing based on Conformance Server Specification.
 """

examples/servers/simple-auth/mcp_simple_auth/auth_server.py

@@ -1,5 +1,4 @@
-"""
+"""Authorization Server for MCP Split Demo.
-Authorization Server for MCP Split Demo.
 
 This server handles OAuth flows, client registration, and token issuance.
 Can be replaced with enterprise authorization servers like Auth0, Entra ID, etc.
@@ -41,8 +40,7 @@ class AuthServerSettings(BaseModel):
 
 
 class SimpleAuthProvider(SimpleOAuthProvider):
-    """
+    """Authorization Server provider with simple demo authentication.
-    Authorization Server provider with simple demo authentication.
 
     This provider:
     1. Issues MCP tokens after simple credential authentication
@@ -98,8 +96,7 @@ def create_authorization_server(server_settings: AuthServerSettings, auth_settin
 
     # Add token introspection endpoint (RFC 7662) for Resource Servers
     async def introspect_handler(request: Request) -> Response:
-        """
+        """Token introspection endpoint for Resource Servers.
-        Token introspection endpoint for Resource Servers.
 
         Resource Servers call this endpoint to validate tokens without
         needing direct access to token storage.
@@ -157,8 +154,7 @@ async def run_server(server_settings: AuthServerSettings, auth_settings: SimpleA
 @click.command()
 @click.option("--port", default=9000, help="Port to listen on")
 def main(port: int) -> int:
-    """
+    """Run the MCP Authorization Server.
-    Run the MCP Authorization Server.
 
     This server handles OAuth flows and can be used by multiple Resource Servers.
 

examples/servers/simple-auth/mcp_simple_auth/legacy_as_server.py

@@ -1,5 +1,4 @@
-"""
+"""Legacy Combined Authorization Server + Resource Server for MCP.
-Legacy Combined Authorization Server + Resource Server for MCP.
 
 This server implements the old spec where MCP servers could act as both AS and RS.
 Used for backwards compatibility testing with the new split AS/RS architecture.
@@ -87,8 +86,7 @@ def create_simple_mcp_server(server_settings: ServerSettings, auth_settings: Sim
 
     @app.tool()
     async def get_time() -> dict[str, Any]:
-        """
+        """Get the current server time.
-        Get the current server time.
 
         This tool demonstrates that system information can be protected
         by OAuth authentication. User must be authenticated to access it.