feat(client): store InitializeResult as initialize_result (#2300)

tests/client/test_client.py

@@ -99,7 +99,7 @@ def app() -> MCPServer:
 async def test_client_is_initialized(app: MCPServer):
     """Test that the client is initialized after entering context."""
     async with Client(app) as client:
-        assert client.server_capabilities == snapshot(
+        assert client.initialize_result.capabilities == snapshot(
             ServerCapabilities(
                 experimental={},
                 prompts=PromptsCapability(list_changed=False),
@@ -107,6 +107,7 @@ async def test_client_is_initialized(app: MCPServer):
                 tools=ToolsCapability(list_changed=False),
             )
         )
+        assert client.initialize_result.server_info.name == "test"
 
 
 async def test_client_with_simple_server(simple_server: Server):

tests/client/test_session.py

@@ -540,8 +540,8 @@ async def test_client_capabilities_with_sampling_tools():
 
 
 @pytest.mark.anyio
-async def test_get_server_capabilities():
-    """Test that get_server_capabilities returns None before init and capabilities after"""
+async def test_initialize_result():
+    """Test that initialize_result is None before init and contains the full result after."""
     client_to_server_send, client_to_server_receive = anyio.create_memory_object_stream[SessionMessage](1)
     server_to_client_send, server_to_client_receive = anyio.create_memory_object_stream[SessionMessage](1)
 
@@ -551,6 +551,8 @@ async def test_get_server_capabilities():
         resources=types.ResourcesCapability(subscribe=True, list_changed=True),
         tools=types.ToolsCapability(list_changed=False),
     )
+    expected_server_info = Implementation(name="mock-server", version="0.1.0")
+    expected_instructions = "Use the tools wisely."
 
     async def mock_server():
         session_message = await client_to_server_receive.receive()
@@ -564,7 +566,8 @@ async def test_get_server_capabilities():
         result = InitializeResult(
             protocol_version=LATEST_PROTOCOL_VERSION,
             capabilities=expected_capabilities,
-            server_info=Implementation(name="mock-server", version="0.1.0"),
+            server_info=expected_server_info,
+            instructions=expected_instructions,
         )
 
         async with server_to_client_send:
@@ -590,21 +593,17 @@ async def test_get_server_capabilities():
         server_to_client_send,
         server_to_client_receive,
     ):
-        assert session.get_server_capabilities() is None
+        assert session.initialize_result is None
 
         tg.start_soon(mock_server)
         await session.initialize()
 
-        capabilities = session.get_server_capabilities()
-        assert capabilities is not None
-        assert capabilities == expected_capabilities
-        assert capabilities.logging is not None
-        assert capabilities.prompts is not None
-        assert capabilities.prompts.list_changed is True
-        assert capabilities.resources is not None
-        assert capabilities.resources.subscribe is True
-        assert capabilities.tools is not None
-        assert capabilities.tools.list_changed is False
+        result = session.initialize_result
+        assert result is not None
+        assert result.server_info == expected_server_info
+        assert result.capabilities == expected_capabilities
+        assert result.instructions == expected_instructions
+        assert result.protocol_version == LATEST_PROTOCOL_VERSION
 
 
 @pytest.mark.anyio

tests/client/transports/test_memory.py

@@ -69,7 +69,7 @@ async def test_with_mcpserver(mcpserver_server: MCPServer):
 async def test_server_is_running(mcpserver_server: MCPServer):
     """Test that the server is running and responding to requests."""
     async with Client(mcpserver_server) as client:
-        assert client.server_capabilities is not None
+        assert client.initialize_result.capabilities.tools is not None
 
 
 async def test_list_tools(mcpserver_server: MCPServer):

tests/server/mcpserver/test_integration.py

@@ -109,8 +109,7 @@ async def elicitation_callback(context: RequestContext[ClientSession], params: E
 async def test_basic_tools() -> None:
     """Test basic tool functionality."""
     async with Client(basic_tool.mcp) as client:
-        assert client.server_capabilities is not None
-        assert client.server_capabilities.tools is not None
+        assert client.initialize_result.capabilities.tools is not None
 
         # Test sum tool
         tool_result = await client.call_tool("sum", {"a": 5, "b": 3})
@@ -128,8 +127,7 @@ async def test_basic_tools() -> None:
 async def test_basic_resources() -> None:
     """Test basic resource functionality."""
     async with Client(basic_resource.mcp) as client:
-        assert client.server_capabilities is not None
-        assert client.server_capabilities.resources is not None
+        assert client.initialize_result.capabilities.resources is not None
 
         # Test document resource
         doc_content = await client.read_resource("file://documents/readme")
@@ -151,8 +149,7 @@ async def test_basic_resources() -> None:
 async def test_basic_prompts() -> None:
     """Test basic prompt functionality."""
     async with Client(basic_prompt.mcp) as client:
-        assert client.server_capabilities is not None
-        assert client.server_capabilities.prompts is not None
+        assert client.initialize_result.capabilities.prompts is not None
 
         # Test review_code prompt
         prompts = await client.list_prompts()
@@ -223,8 +220,7 @@ async def test_tool_progress() -> None:
 async def test_sampling() -> None:
     """Test sampling (LLM interaction) functionality."""
     async with Client(sampling.mcp, sampling_callback=sampling_callback) as client:
-        assert client.server_capabilities is not None
-        assert client.server_capabilities.tools is not None
+        assert client.initialize_result.capabilities.tools is not None
 
         # Test sampling tool
         sampling_result = await client.call_tool("generate_poem", {"topic": "nature"})
@@ -294,9 +290,8 @@ async def test_notifications() -> None:
 async def test_completion() -> None:
     """Test completion (autocomplete) functionality."""
     async with Client(completion.mcp) as client:
-        assert client.server_capabilities is not None
-        assert client.server_capabilities.resources is not None
-        assert client.server_capabilities.prompts is not None
+        assert client.initialize_result.capabilities.resources is not None
+        assert client.initialize_result.capabilities.prompts is not None
 
         # Test resource completion
         completion_result = await client.complete(