Allow passing initialization options to a session

We need a way for servers to pass initialization options to the session.
This is the beginning of this.

Author: dsp-ant

mcp_python/server/__main__.py

@@ -1,10 +1,11 @@
 import logging
 import sys
-
+import importlib.metadata
 import anyio
 
-from mcp_python.server.session import ServerSession
+from mcp_python.server.session import InitializationOptions, ServerSession
 from mcp_python.server.stdio import stdio_server
+from mcp_python.types import ServerCapabilities
 
 if not sys.warnoptions:
     import warnings
@@ -26,8 +27,9 @@ async def receive_loop(session: ServerSession):
 
 
 async def main():
+    version = importlib.metadata.version("mcp_python")
     async with stdio_server() as (read_stream, write_stream):
-        async with ServerSession(read_stream, write_stream) as session, write_stream:
+        async with ServerSession(read_stream, write_stream, InitializationOptions(server_name="mcp_python", server_version=version, capabilities=ServerCapabilities())) as session, write_stream:
             await receive_loop(session)
 
 

mcp_python/server/session.py

@@ -1,5 +1,6 @@
 from enum import Enum
 from typing import Any
+from dataclasses import dataclass
 
 import anyio
 import anyio.lowlevel
@@ -37,6 +38,12 @@ class InitializationState(Enum):
     Initialized = 3
 
 
+@dataclass
+class InitializationOptions:
+    server_name: str
+    server_version: str
+    capabilities: ServerCapabilities
+
 class ServerSession(
     BaseSession[
         ServerRequest,
@@ -52,9 +59,11 @@ def __init__(
         self,
         read_stream: MemoryObjectReceiveStream[JSONRPCMessage | Exception],
         write_stream: MemoryObjectSendStream[JSONRPCMessage],
+        init_options: InitializationOptions
     ) -> None:
         super().__init__(read_stream, write_stream, ClientRequest, ClientNotification)
         self._initialization_state = InitializationState.NotInitialized
+        self._init_options = init_options
 
     async def _received_request(
         self, responder: RequestResponder[ClientRequest, ServerResult]
@@ -66,15 +75,10 @@ async def _received_request(
                     ServerResult(
                         InitializeResult(
                             protocolVersion=SUPPORTED_PROTOCOL_VERSION,
-                            capabilities=ServerCapabilities(
-                                logging=None,
-                                resources=None,
-                                tools=None,
-                                experimental=None,
-                                prompts={},
-                            ),
+                            capabilities=self._init_options.capabilities,
                             serverInfo=Implementation(
-                                name="mcp_python", version="0.1.0"
+                                name=self._init_options.server_name,
+                                version=self._init_options.server_version
                             ),
                         )
                     )

tests/server/test_session.py

@@ -2,11 +2,12 @@
 import pytest
 
 from mcp_python.client.session import ClientSession
-from mcp_python.server.session import ServerSession
+from mcp_python.server.session import InitializationOptions, ServerSession
 from mcp_python.types import (
     ClientNotification,
     InitializedNotification,
     JSONRPCMessage,
+    ServerCapabilities,
 )
 
 
@@ -30,7 +31,7 @@ async def run_server():
         nonlocal received_initialized
 
         async with ServerSession(
-            client_to_server_receive, server_to_client_send
+            client_to_server_receive, server_to_client_send, InitializationOptions(server_name='mcp_python', server_version='0.1.0', capabilities=ServerCapabilities())
         ) as server_session:
             async for message in server_session.incoming_messages:
                 if isinstance(message, Exception):