feat: support setting title and description for server

Add support for the `title` and `description` fields in the
`Implementation` type, allowing servers to provide human-readable
metadata during initialization.

Changes:
- Add `description` field to `types.Implementation`
- Add `server_title` and `server_description` to `InitializationOptions`
- Wire up title/description through `Server` constructor and session
- Add test for title and description passthrough

Github-Issue:#1783

Author: maxisbey

src/mcp/server/lowlevel/server.py

@@ -139,6 +139,8 @@ def __init__(
         self,
         name: str,
         version: str | None = None,
+        title: str | None = None,
+        description: str | None = None,
         instructions: str | None = None,
         website_url: str | None = None,
         icons: list[types.Icon] | None = None,
@@ -149,6 +151,8 @@ def __init__(
     ):
         self.name = name
         self.version = version
+        self.title = title
+        self.description = description
         self.instructions = instructions
         self.website_url = website_url
         self.icons = icons
@@ -186,6 +190,8 @@ def pkg_version(package: str) -> str:
                 experimental_capabilities or {},
             ),
             instructions=self.instructions,
+            server_title=self.title,
+            server_description=self.description,
             website_url=self.website_url,
             icons=self.icons,
         )

src/mcp/server/models.py

@@ -16,5 +16,7 @@ class InitializationOptions(BaseModel):
     server_version: str
     capabilities: ServerCapabilities
     instructions: str | None = None
+    server_title: str | None = None
+    server_description: str | None = None
     website_url: str | None = None
     icons: list[Icon] | None = None

src/mcp/server/session.py

@@ -176,7 +176,9 @@ async def _received_request(self, responder: RequestResponder[types.ClientReques
                                 capabilities=self._init_options.capabilities,
                                 serverInfo=types.Implementation(
                                     name=self._init_options.server_name,
+                                    title=self._init_options.server_title,
                                     version=self._init_options.server_version,
+                                    description=self._init_options.server_description,
                                     websiteUrl=self._init_options.website_url,
                                     icons=self._init_options.icons,
                                 ),

src/mcp/types.py

@@ -265,6 +265,15 @@ class Implementation(BaseMetadata):
 
     version: str
 
+    description: str | None = None
+    """
+    An optional human-readable description of what this implementation does.
+
+    This can be used by clients or servers to provide context about their purpose
+    and capabilities. For example, a server might describe the types of resources
+    or tools it provides, while a client might describe its intended use case.
+    """
+
     websiteUrl: str | None = None
     """An optional URL of the website for this implementation."""
 

tests/server/test_session.py

@@ -83,6 +83,62 @@ async def run_server():
     assert received_initialized
 
 
+@pytest.mark.anyio
+async def test_server_session_initialize_with_title_and_description():
+    """Test that server_title and server_description are passed through to serverInfo."""
+    server_to_client_send, server_to_client_receive = anyio.create_memory_object_stream[SessionMessage](1)
+    client_to_server_send, client_to_server_receive = anyio.create_memory_object_stream[SessionMessage](1)
+
+    async def message_handler(
+        message: RequestResponder[types.ServerRequest, types.ClientResult] | types.ServerNotification | Exception,
+    ) -> None:
+        if isinstance(message, Exception):
+            raise message
+
+    async def run_server():
+        async with ServerSession(
+            client_to_server_receive,
+            server_to_client_send,
+            InitializationOptions(
+                server_name="test-server",
+                server_version="1.0.0",
+                server_title="Test Server Title",
+                server_description="A description of what this server does.",
+                capabilities=ServerCapabilities(),
+            ),
+        ) as server_session:
+            async for message in server_session.incoming_messages:  # pragma: no branch
+                if isinstance(message, Exception):  # pragma: no cover
+                    raise message
+
+                if isinstance(message, ClientNotification) and isinstance(
+                    message.root, InitializedNotification
+                ):  # pragma: no branch
+                    return
+
+    result: types.InitializeResult | None = None
+    try:
+        async with (
+            ClientSession(
+                server_to_client_receive,
+                client_to_server_send,
+                message_handler=message_handler,
+            ) as client_session,
+            anyio.create_task_group() as tg,
+        ):
+            tg.start_soon(run_server)
+
+            result = await client_session.initialize()
+    except anyio.ClosedResourceError:  # pragma: no cover
+        pass
+
+    assert result is not None
+    assert result.serverInfo.name == "test-server"
+    assert result.serverInfo.title == "Test Server Title"
+    assert result.serverInfo.version == "1.0.0"
+    assert result.serverInfo.description == "A description of what this server does."
+
+
 @pytest.mark.anyio
 async def test_server_capabilities():
     server = Server("test")