Add strict mode to pyright (#315)

* Add strict mode to pyright

* Apply UP rule

* fix readme

* More correct

* Leave wrong Context for now

* Add strict mode to pyright

* Apply UP rule

* fix readme

* fix

* ignore

README.md

@@ -16,8 +16,11 @@
 <!-- omit in toc -->
 ## Table of Contents
 
+- [MCP Python SDK](#mcp-python-sdk)
   - [Overview](#overview)
   - [Installation](#installation)
+    - [Adding MCP to your python project](#adding-mcp-to-your-python-project)
+    - [Running the standalone MCP development tools](#running-the-standalone-mcp-development-tools)
   - [Quickstart](#quickstart)
   - [What is MCP?](#what-is-mcp)
   - [Core Concepts](#core-concepts)
@@ -143,8 +146,8 @@ The FastMCP server is your core interface to the MCP protocol. It handles connec
 ```python
 # Add lifespan support for startup/shutdown with strong typing
 from contextlib import asynccontextmanager
+from collections.abc import AsyncIterator
 from dataclasses import dataclass
-from typing import AsyncIterator
 
 from fake_database import Database  # Replace with your actual DB type
 
@@ -442,7 +445,7 @@ For more control, you can use the low-level server implementation directly. This
 
 ```python
 from contextlib import asynccontextmanager
-from typing import AsyncIterator
+from collections.abc import AsyncIterator
 
 from fake_database import Database  # Replace with your actual DB type
 

pyproject.toml

@@ -76,13 +76,11 @@ packages = ["src/mcp"]
 include = ["src/mcp", "tests"]
 venvPath = "."
 venv = ".venv"
-strict = [
+strict = ["src/mcp/**/*.py"]
-    "src/mcp/server/fastmcp/tools/base.py",
+exclude = ["src/mcp/types.py"]
-    "src/mcp/client/*.py"
-]
 
 [tool.ruff.lint]
-select = ["E", "F", "I"]
+select = ["E", "F", "I", "UP"]
 ignore = []
 
 [tool.ruff]

src/mcp/cli/claude.py

@@ -4,6 +4,7 @@ import json
 import os
 import sys
 from pathlib import Path
+from typing import Any
 
 from mcp.server.fastmcp.utilities.logging import get_logger
 
@@ -116,10 +117,7 @@ def update_claude_config(
         # Add fastmcp run command
         args.extend(["mcp", "run", file_spec])
 
-        server_config = {
+        server_config: dict[str, Any] = {"command": "uv", "args": args}
-            "command": "uv",
-            "args": args,
-        }
 
         # Add environment variables if specified
         if env_vars:

src/mcp/client/websocket.py

@@ -1,7 +1,7 @@
 import json
 import logging
+from collections.abc import AsyncGenerator
 from contextlib import asynccontextmanager
-from typing import AsyncGenerator
 
 import anyio
 from anyio.streams.memory import MemoryObjectReceiveStream, MemoryObjectSendStream

src/mcp/server/fastmcp/prompts/base.py

@@ -2,8 +2,8 @@
 
 import inspect
 import json
-from collections.abc import Callable
+from collections.abc import Awaitable, Callable, Sequence
-from typing import Any, Awaitable, Literal, Sequence
+from typing import Any, Literal
 
 import pydantic_core
 from pydantic import BaseModel, Field, TypeAdapter, validate_call
@@ -19,7 +19,7 @@ class Message(BaseModel):
     role: Literal["user", "assistant"]
     content: CONTENT_TYPES
 
-    def __init__(self, content: str | CONTENT_TYPES, **kwargs):
+    def __init__(self, content: str | CONTENT_TYPES, **kwargs: Any):
         if isinstance(content, str):
             content = TextContent(type="text", text=content)
         super().__init__(content=content, **kwargs)
@@ -30,7 +30,7 @@ class UserMessage(Message):
 
     role: Literal["user", "assistant"] = "user"
 
-    def __init__(self, content: str | CONTENT_TYPES, **kwargs):
+    def __init__(self, content: str | CONTENT_TYPES, **kwargs: Any):
         super().__init__(content=content, **kwargs)
 
 
@@ -39,11 +39,13 @@ class AssistantMessage(Message):
 
     role: Literal["user", "assistant"] = "assistant"
 
-    def __init__(self, content: str | CONTENT_TYPES, **kwargs):
+    def __init__(self, content: str | CONTENT_TYPES, **kwargs: Any):
         super().__init__(content=content, **kwargs)
 
 
-message_validator = TypeAdapter(UserMessage | AssistantMessage)
+message_validator = TypeAdapter[UserMessage | AssistantMessage](
+    UserMessage | AssistantMessage
+)
 
 SyncPromptResult = (
     str | Message | dict[str, Any] | Sequence[str | Message | dict[str, Any]]
@@ -73,12 +75,12 @@ class Prompt(BaseModel):
     arguments: list[PromptArgument] | None = Field(
         None, description="Arguments that can be passed to the prompt"
     )
-    fn: Callable = Field(exclude=True)
+    fn: Callable[..., PromptResult | Awaitable[PromptResult]] = Field(exclude=True)
 
     @classmethod
     def from_function(
         cls,
-        fn: Callable[..., PromptResult],
+        fn: Callable[..., PromptResult | Awaitable[PromptResult]],
         name: str | None = None,
         description: str | None = None,
     ) -> "Prompt":
@@ -99,7 +101,7 @@ class Prompt(BaseModel):
         parameters = TypeAdapter(fn).json_schema()
 
         # Convert parameters to PromptArguments
-        arguments = []
+        arguments: list[PromptArgument] = []
         if "properties" in parameters:
             for param_name, param in parameters["properties"].items():
                 required = param_name in parameters.get("required", [])
@@ -138,25 +140,23 @@ class Prompt(BaseModel):
                 result = await result
 
             # Validate messages
-            if not isinstance(result, (list, tuple)):
+            if not isinstance(result, list | tuple):
                 result = [result]
 
             # Convert result to messages
-            messages = []
+            messages: list[Message] = []
-            for msg in result:
+            for msg in result:  # type: ignore[reportUnknownVariableType]
                 try:
                     if isinstance(msg, Message):
                         messages.append(msg)
                     elif isinstance(msg, dict):
-                        msg = message_validator.validate_python(msg)
+                        messages.append(message_validator.validate_python(msg))
-                        messages.append(msg)
                     elif isinstance(msg, str):
-                        messages.append(
+                        content = TextContent(type="text", text=msg)
-                            UserMessage(content=TextContent(type="text", text=msg))
+                        messages.append(UserMessage(content=content))
-                        )
                     else:
-                        msg = json.dumps(pydantic_core.to_jsonable_python(msg))
+                        content = json.dumps(pydantic_core.to_jsonable_python(msg))
-                        messages.append(Message(role="user", content=msg))
+                        messages.append(Message(role="user", content=content))
                 except Exception:
                     raise ValueError(
                         f"Could not convert prompt result to message: {msg}"

src/mcp/server/fastmcp/resources/resource_manager.py

@@ -1,6 +1,7 @@
 """Resource manager functionality."""
 
-from typing import Callable
+from collections.abc import Callable
+from typing import Any
 
 from pydantic import AnyUrl
 
@@ -47,7 +48,7 @@ class ResourceManager:
 
     def add_template(
         self,
-        fn: Callable,
+        fn: Callable[..., Any],
         uri_template: str,
         name: str | None = None,
         description: str | None = None,

src/mcp/server/fastmcp/resources/templates.py

@@ -1,8 +1,11 @@
 """Resource template functionality."""
 
+from __future__ import annotations
+
 import inspect
 import re
-from typing import Any, Callable
+from collections.abc import Callable
+from typing import Any
 
 from pydantic import BaseModel, Field, TypeAdapter, validate_call
 
@@ -20,18 +23,20 @@ class ResourceTemplate(BaseModel):
     mime_type: str = Field(
         default="text/plain", description="MIME type of the resource content"
     )
-    fn: Callable = Field(exclude=True)
+    fn: Callable[..., Any] = Field(exclude=True)
-    parameters: dict = Field(description="JSON schema for function parameters")
+    parameters: dict[str, Any] = Field(
+        description="JSON schema for function parameters"
+    )
 
     @classmethod
     def from_function(
         cls,
-        fn: Callable,
+        fn: Callable[..., Any],
         uri_template: str,
         name: str | None = None,
         description: str | None = None,
         mime_type: str | None = None,
-    ) -> "ResourceTemplate":
+    ) -> ResourceTemplate:
         """Create a template from a function."""
         func_name = name or fn.__name__
         if func_name == "<lambda>":

src/mcp/server/fastmcp/server.py

@@ -5,13 +5,13 @@ from __future__ import annotations as _annotations
 import inspect
 import json
 import re
-from collections.abc import AsyncIterator, Iterable
+from collections.abc import AsyncIterator, Callable, Iterable, Sequence
 from contextlib import (
     AbstractAsyncContextManager,
     asynccontextmanager,
 )
 from itertools import chain
-from typing import Any, Callable, Generic, Literal, Sequence
+from typing import Any, Generic, Literal
 
 import anyio
 import pydantic_core
@@ -20,6 +20,7 @@ from pydantic import BaseModel, Field
 from pydantic.networks import AnyUrl
 from pydantic_settings import BaseSettings, SettingsConfigDict
 from starlette.applications import Starlette
+from starlette.requests import Request
 from starlette.routing import Mount, Route
 
 from mcp.server.fastmcp.exceptions import ResourceError
@@ -88,13 +89,13 @@ class Settings(BaseSettings, Generic[LifespanResultT]):
     )
 
     lifespan: (
-        Callable[["FastMCP"], AbstractAsyncContextManager[LifespanResultT]] | None
+        Callable[[FastMCP], AbstractAsyncContextManager[LifespanResultT]] | None
     ) = Field(None, description="Lifespan context manager")
 
 
 def lifespan_wrapper(
     app: FastMCP,
-    lifespan: Callable[["FastMCP"], AbstractAsyncContextManager[LifespanResultT]],
+    lifespan: Callable[[FastMCP], AbstractAsyncContextManager[LifespanResultT]],
 ) -> Callable[[MCPServer[LifespanResultT]], AbstractAsyncContextManager[object]]:
     @asynccontextmanager
     async def wrap(s: MCPServer[LifespanResultT]) -> AsyncIterator[object]:
@@ -179,7 +180,7 @@ class FastMCP:
             for info in tools
         ]
 
-    def get_context(self) -> "Context[ServerSession, object]":
+    def get_context(self) -> Context[ServerSession, object]:
         """
         Returns a Context object. Note that the context will only be valid
         during a request; outside a request, most methods will error.
@@ -478,9 +479,11 @@ class FastMCP:
         """Return an instance of the SSE server app."""
         sse = SseServerTransport("/messages/")
 
-        async def handle_sse(request):
+        async def handle_sse(request: Request) -> None:
             async with sse.connect_sse(
-                request.scope, request.receive, request._send
+                request.scope,
+                request.receive,
+                request._send,  # type: ignore[reportPrivateUsage]
             ) as streams:
                 await self._mcp_server.run(
                     streams[0],
@@ -535,14 +538,14 @@ def _convert_to_content(
     if result is None:
         return []
 
-    if isinstance(result, (TextContent, ImageContent, EmbeddedResource)):
+    if isinstance(result, TextContent | ImageContent | EmbeddedResource):
         return [result]
 
     if isinstance(result, Image):
         return [result.to_image_content()]
 
-    if isinstance(result, (list, tuple)):
+    if isinstance(result, list | tuple):
-        return list(chain.from_iterable(_convert_to_content(item) for item in result))
+        return list(chain.from_iterable(_convert_to_content(item) for item in result))  # type: ignore[reportUnknownVariableType]
 
     if not isinstance(result, str):
         try:

src/mcp/server/fastmcp/tools/base.py

@@ -1,11 +1,11 @@
 from __future__ import annotations as _annotations
 
 import inspect
-from typing import TYPE_CHECKING, Any, Callable
+from collections.abc import Callable
+from typing import TYPE_CHECKING, Any
 
 from pydantic import BaseModel, Field
 
-import mcp.server.fastmcp
 from mcp.server.fastmcp.exceptions import ToolError
 from mcp.server.fastmcp.utilities.func_metadata import FuncMetadata, func_metadata
 
@@ -38,8 +38,10 @@ class Tool(BaseModel):
         name: str | None = None,
         description: str | None = None,
         context_kwarg: str | None = None,
-    ) -> "Tool":
+    ) -> Tool:
         """Create a Tool from a function."""
+        from mcp.server.fastmcp import Context
+
         func_name = name or fn.__name__
 
         if func_name == "<lambda>":
@@ -48,11 +50,10 @@ class Tool(BaseModel):
         func_doc = description or fn.__doc__ or ""
         is_async = inspect.iscoroutinefunction(fn)
 
-        # Find context parameter if it exists
         if context_kwarg is None:
             sig = inspect.signature(fn)
             for param_name, param in sig.parameters.items():
-                if param.annotation is mcp.server.fastmcp.Context:
+                if param.annotation is Context:
                     context_kwarg = param_name
                     break
 

src/mcp/server/fastmcp/tools/tool_manager.py

@@ -32,7 +32,7 @@ class ToolManager:
 
     def add_tool(
         self,
-        fn: Callable,
+        fn: Callable[..., Any],
         name: str | None = None,
         description: str | None = None,
     ) -> Tool:

src/mcp/server/fastmcp/utilities/func_metadata.py

@@ -80,7 +80,7 @@ class FuncMetadata(BaseModel):
         dicts (JSON objects) as JSON strings, which can be pre-parsed here.
         """
         new_data = data.copy()  # Shallow copy
-        for field_name, field_info in self.arg_model.model_fields.items():
+        for field_name, _field_info in self.arg_model.model_fields.items():
             if field_name not in data.keys():
                 continue
             if isinstance(data[field_name], str):
@@ -177,7 +177,9 @@ def func_metadata(
 
 
 def _get_typed_annotation(annotation: Any, globalns: dict[str, Any]) -> Any:
-    def try_eval_type(value, globalns, localns):
+    def try_eval_type(
+        value: Any, globalns: dict[str, Any], localns: dict[str, Any]
+    ) -> tuple[Any, bool]:
         try:
             return eval_type_backport(value, globalns, localns), True
         except NameError:

src/mcp/server/fastmcp/utilities/logging.py

@@ -24,7 +24,7 @@ def configure_logging(
     Args:
         level: the log level to use
     """
-    handlers = []
+    handlers: list[logging.Handler] = []
     try:
         from rich.console import Console
         from rich.logging import RichHandler

src/mcp/server/lowlevel/server.py

@@ -69,9 +69,9 @@ from __future__ import annotations as _annotations
 import contextvars
 import logging
 import warnings
-from collections.abc import Awaitable, Callable, Iterable
+from collections.abc import AsyncIterator, Awaitable, Callable, Iterable
 from contextlib import AbstractAsyncContextManager, AsyncExitStack, asynccontextmanager
-from typing import Any, AsyncIterator, Generic, TypeVar
+from typing import Any, Generic, TypeVar
 
 import anyio
 from anyio.streams.memory import MemoryObjectReceiveStream, MemoryObjectSendStream
@@ -155,9 +155,7 @@ class Server(Generic[LifespanResultT]):
             try:
                 from importlib.metadata import version
 
-                v = version(package)
+                return version(package)
-                if v is not None:
-                    return v
             except Exception:
                 pass
 
@@ -320,7 +318,6 @@ class Server(Generic[LifespanResultT]):
                         contents_list = [
                             create_content(content_item.content, content_item.mime_type)
                             for content_item in contents
-                            if isinstance(content_item, ReadResourceContents)
                         ]
                         return types.ServerResult(
                             types.ReadResourceResult(
@@ -511,7 +508,8 @@ class Server(Generic[LifespanResultT]):
         raise_exceptions: bool = False,
     ):
         with warnings.catch_warnings(record=True) as w:
-            match message:
+            # TODO(Marcelo): We should be checking if message is Exception here.
+            match message:  # type: ignore[reportMatchNotExhaustive]
                 case (
                     RequestResponder(request=types.ClientRequest(root=req)) as responder
                 ):
@@ -527,7 +525,7 @@ class Server(Generic[LifespanResultT]):
 
     async def _handle_request(
         self,
-        message: RequestResponder,
+        message: RequestResponder[types.ClientRequest, types.ServerResult],
         req: Any,
         session: ServerSession,
         lifespan_context: LifespanResultT,

src/mcp/shared/memory.py

@@ -2,9 +2,10 @@
 In-memory transports
 """
 
+from collections.abc import AsyncGenerator
 from contextlib import asynccontextmanager
 from datetime import timedelta
-from typing import AsyncGenerator
+from typing import Any
 
 import anyio
 from anyio.streams.memory import MemoryObjectReceiveStream, MemoryObjectSendStream
@@ -52,7 +53,7 @@ async def create_client_server_memory_streams() -> (
 
 @asynccontextmanager
 async def create_connected_server_and_client_session(
-    server: Server,
+    server: Server[Any],
     read_timeout_seconds: timedelta | None = None,
     sampling_callback: SamplingFnT | None = None,
     list_roots_callback: ListRootsFnT | None = None,

src/mcp/shared/progress.py

@@ -1,10 +1,19 @@
+from collections.abc import Generator
 from contextlib import contextmanager
 from dataclasses import dataclass, field
+from typing import Generic
 
 from pydantic import BaseModel
 
 from mcp.shared.context import RequestContext
-from mcp.shared.session import BaseSession
+from mcp.shared.session import (
+    BaseSession,
+    ReceiveNotificationT,
+    ReceiveRequestT,
+    SendNotificationT,
+    SendRequestT,
+    SendResultT,
+)
 from mcp.types import ProgressToken
 
 
@@ -14,8 +23,22 @@ class Progress(BaseModel):
 
 
 @dataclass
-class ProgressContext:
+class ProgressContext(
-    session: BaseSession
+    Generic[
+        SendRequestT,
+        SendNotificationT,
+        SendResultT,
+        ReceiveRequestT,
+        ReceiveNotificationT,
+    ]
+):
+    session: BaseSession[
+        SendRequestT,
+        SendNotificationT,
+        SendResultT,
+        ReceiveRequestT,
+        ReceiveNotificationT,
+    ]
     progress_token: ProgressToken
     total: float | None
     current: float = field(default=0.0, init=False)
@@ -29,7 +52,27 @@ class ProgressContext:
 
 
 @contextmanager
-def progress(ctx: RequestContext, total: float | None = None):
+def progress(
+    ctx: RequestContext[
+        BaseSession[
+            SendRequestT,
+            SendNotificationT,
+            SendResultT,
+            ReceiveRequestT,
+            ReceiveNotificationT,
+        ]
+    ],
+    total: float | None = None,
+) -> Generator[
+    ProgressContext[
+        SendRequestT,
+        SendNotificationT,
+        SendResultT,
+        ReceiveRequestT,
+        ReceiveNotificationT,
+    ],
+    None,
+]:
     if ctx.meta is None or ctx.meta.progressToken is None:
         raise ValueError("No progress token provided")
 

src/mcp/shared/session.py

@@ -1,7 +1,9 @@
 import logging
+from collections.abc import Callable
 from contextlib import AsyncExitStack
 from datetime import timedelta
-from typing import Any, Callable, Generic, TypeVar
+from types import TracebackType
+from typing import Any, Generic, TypeVar
 
 import anyio
 import anyio.lowlevel
@@ -86,7 +88,12 @@ class RequestResponder(Generic[ReceiveRequestT, SendResultT]):
         self._cancel_scope.__enter__()
         return self
 
-    def __exit__(self, exc_type, exc_val, exc_tb) -> None:
+    def __exit__(
+        self,
+        exc_type: type[BaseException] | None,
+        exc_val: BaseException | None,
+        exc_tb: TracebackType | None,
+    ) -> None:
         """Exit the context manager, performing cleanup and notifying completion."""
         try:
             if self._completed:
@@ -112,7 +119,7 @@ class RequestResponder(Generic[ReceiveRequestT, SendResultT]):
         if not self.cancelled:
             self._completed = True
 
-            await self._session._send_response(
+            await self._session._send_response(  # type: ignore[reportPrivateUsage]
                 request_id=self.request_id, response=response
             )
 
@@ -126,7 +133,7 @@ class RequestResponder(Generic[ReceiveRequestT, SendResultT]):
         self._cancel_scope.cancel()
         self._completed = True  # Mark as completed so it's removed from in_flight
         # Send an error response to indicate cancellation
-        await self._session._send_response(
+        await self._session._send_response(  # type: ignore[reportPrivateUsage]
             request_id=self.request_id,
             response=ErrorData(code=0, message="Request cancelled", data=None),
         )
@@ -137,7 +144,7 @@ class RequestResponder(Generic[ReceiveRequestT, SendResultT]):
 
     @property
     def cancelled(self) -> bool:
-        return self._cancel_scope is not None and self._cancel_scope.cancel_called
+        return self._cancel_scope.cancel_called
 
 
 class BaseSession(
@@ -202,7 +209,12 @@ class BaseSession(
         self._task_group.start_soon(self._receive_loop)
         return self
 
-    async def __aexit__(self, exc_type, exc_val, exc_tb):
+    async def __aexit__(
+        self,
+        exc_type: type[BaseException] | None,
+        exc_val: BaseException | None,
+        exc_tb: TracebackType | None,
+    ) -> bool | None:
         await self._exit_stack.aclose()
         # Using BaseSession as a context manager should not block on exit (this
         # would be very surprising behavior), so make sure to cancel the tasks
@@ -324,7 +336,7 @@ class BaseSession(
 
                     self._in_flight[responder.request_id] = responder
                     await self._received_request(responder)
-                    if not responder._completed:
+                    if not responder._completed:  # type: ignore[reportPrivateUsage]
                         await self._incoming_message_stream_writer.send(responder)
 
                 elif isinstance(message.root, JSONRPCNotification):

src/mcp/types.py

@@ -1,7 +1,7 @@
+from collections.abc import Callable
 from typing import (
     Annotated,
     Any,
-    Callable,
     Generic,
     Literal,
     TypeAlias,
@@ -89,6 +89,7 @@ class Notification(BaseModel, Generic[NotificationParamsT, MethodT]):
     """Base class for JSON-RPC notifications."""
 
     method: MethodT
+    params: NotificationParamsT
     model_config = ConfigDict(extra="allow")
 
 
@@ -1010,7 +1011,9 @@ class CancelledNotificationParams(NotificationParams):
     model_config = ConfigDict(extra="allow")
 
 
-class CancelledNotification(Notification):
+class CancelledNotification(
+    Notification[CancelledNotificationParams, Literal["notifications/cancelled"]]
+):
     """
     This notification can be sent by either side to indicate that it is cancelling a
     previously-issued request.

tests/client/test_config.py

@@ -1,5 +1,6 @@
 import json
 import subprocess
+from pathlib import Path
 from unittest.mock import patch
 
 import pytest
@@ -8,7 +9,7 @@ from mcp.cli.claude import update_claude_config
 
 
 @pytest.fixture
-def temp_config_dir(tmp_path):
+def temp_config_dir(tmp_path: Path):
     """Create a temporary Claude config directory."""
     config_dir = tmp_path / "Claude"
     config_dir.mkdir()
@@ -16,23 +17,20 @@ def temp_config_dir(tmp_path):
 
 
 @pytest.fixture
-def mock_config_path(temp_config_dir):
+def mock_config_path(temp_config_dir: Path):
     """Mock get_claude_config_path to return our temporary directory."""
     with patch("mcp.cli.claude.get_claude_config_path", return_value=temp_config_dir):
         yield temp_config_dir
 
 
-def test_command_execution(mock_config_path):
+def test_command_execution(mock_config_path: Path):
     """Test that the generated command can actually be executed."""
     # Setup
     server_name = "test_server"
     file_spec = "test_server.py:app"
 
     # Update config
-    success = update_claude_config(
+    success = update_claude_config(file_spec=file_spec, server_name=server_name)
-        file_spec=file_spec,
-        server_name=server_name,
-    )
     assert success
 
     # Read the generated config

tests/client/test_list_roots_callback.py

@@ -7,11 +7,7 @@ from mcp.shared.context import RequestContext
 from mcp.shared.memory import (
     create_connected_server_and_client_session as create_session,
 )
-from mcp.types import (
+from mcp.types import ListRootsResult, Root, TextContent
-    ListRootsResult,
-    Root,
-    TextContent,
-)
 
 
 @pytest.mark.anyio
@@ -39,7 +35,7 @@ async def test_list_roots_callback():
         return callback_return
 
     @server.tool("test_list_roots")
-    async def test_list_roots(context: Context, message: str):
+    async def test_list_roots(context: Context, message: str):  # type: ignore[reportUnknownMemberType]
         roots = await context.session.list_roots()
         assert roots == callback_return
         return True

tests/client/test_logging_callback.py

@@ -1,4 +1,4 @@
-from typing import List, Literal
+from typing import Literal
 
 import anyio
 import pytest
@@ -14,7 +14,7 @@ from mcp.types import (
 
 class LoggingCollector:
     def __init__(self):
-        self.log_messages: List[LoggingMessageNotificationParams] = []
+        self.log_messages: list[LoggingMessageNotificationParams] = []
 
     async def __call__(self, params: LoggingMessageNotificationParams) -> None:
         self.log_messages.append(params)

tests/issues/test_88_random_error.py

@@ -1,8 +1,8 @@
 """Test to reproduce issue #88: Random error thrown on response."""
 
+from collections.abc import Sequence
 from datetime import timedelta
 from pathlib import Path
-from typing import Sequence
 
 import anyio
 import pytest

tests/server/fastmcp/test_server.py

@@ -1,6 +1,6 @@
 import base64
 from pathlib import Path
-from typing import TYPE_CHECKING, Union
+from typing import TYPE_CHECKING
 
 import pytest
 from pydantic import AnyUrl
@@ -114,7 +114,7 @@ def image_tool_fn(path: str) -> Image:
     return Image(path)
 
 
-def mixed_content_tool_fn() -> list[Union[TextContent, ImageContent]]:
+def mixed_content_tool_fn() -> list[TextContent | ImageContent]:
     return [
         TextContent(type="text", text="Hello"),
         ImageContent(type="image", data="abc", mimeType="image/png"),

tests/server/fastmcp/test_tool_manager.py

@@ -1,6 +1,5 @@
 import json
 import logging
-from typing import Optional
 
 import pytest
 from pydantic import BaseModel
@@ -296,7 +295,7 @@ class TestContextHandling:
         """Test that context is optional when calling tools."""
         from mcp.server.fastmcp import Context
 
-        def tool_with_context(x: int, ctx: Optional[Context] = None) -> str:
+        def tool_with_context(x: int, ctx: Context | None = None) -> str:
             return str(x)
 
         manager = ToolManager()

tests/server/test_lifespan.py

@@ -1,7 +1,7 @@
 """Tests for lifespan functionality in both low-level and FastMCP servers."""
 
+from collections.abc import AsyncIterator
 from contextlib import asynccontextmanager
-from typing import AsyncIterator
 
 import anyio
 import pytest

tests/shared/test_session.py

@@ -1,4 +1,4 @@
-from typing import AsyncGenerator
+from collections.abc import AsyncGenerator
 
 import anyio
 import pytest

tests/shared/test_sse.py

@@ -1,7 +1,7 @@
 import multiprocessing
 import socket
 import time
-from typing import AsyncGenerator, Generator
+from collections.abc import AsyncGenerator, Generator
 
 import anyio
 import httpx
@@ -139,7 +139,7 @@ def server(server_port: int) -> Generator[None, None, None]:
             attempt += 1
     else:
         raise RuntimeError(
-            "Server failed to start after {} attempts".format(max_attempts)
+            f"Server failed to start after {max_attempts} attempts"
         )
 
     yield

tests/shared/test_ws.py

@@ -1,7 +1,7 @@
 import multiprocessing
 import socket
 import time
-from typing import AsyncGenerator, Generator
+from collections.abc import AsyncGenerator, Generator
 
 import anyio
 import pytest
@@ -135,7 +135,7 @@ def server(server_port: int) -> Generator[None, None, None]:
             attempt += 1
     else:
         raise RuntimeError(
-            "Server failed to start after {} attempts".format(max_attempts)
+            f"Server failed to start after {max_attempts} attempts"
         )
 
     yield