Remove helper types

The helper types in mcp.server.types got really confusioning during
implementation as they overlapped with mcp.types. I now believe it
is better if we stay more low level to the spec types.

To do this, we now only use mcp.types everywhere. We renamed mcp.server.types
to mcp.server.models and removed it to the absolute minimum.

Author: dsp-ant

src/mcp/server/__init__.py

@@ -7,14 +7,18 @@
 from anyio.streams.memory import MemoryObjectReceiveStream, MemoryObjectSendStream
 from pydantic import AnyUrl
 
-from mcp.server import types
+from mcp.server.models import InitializationOptions
 from mcp.server.session import ServerSession
 from mcp.server.stdio import stdio_server as stdio_server
 from mcp.shared.context import RequestContext
 from mcp.shared.session import RequestResponder
 from mcp.types import (
     METHOD_NOT_FOUND,
     CallToolRequest,
+    GetPromptResult,
+    GetPromptRequest,
+    GetPromptResult,
+    ImageContent,
     ClientNotification,
     ClientRequest,
     CompleteRequest,
@@ -84,7 +88,7 @@ def create_initialization_options(
         self,
         notification_options: NotificationOptions | None = None,
         experimental_capabilities: dict[str, dict[str, Any]] | None = None,
-    ) -> types.InitializationOptions:
+    ) -> InitializationOptions:
         """Create initialization options from this server instance."""
 
         def pkg_version(package: str) -> str:
@@ -99,7 +103,7 @@ def pkg_version(package: str) -> str:
 
             return "unknown"
 
-        return types.InitializationOptions(
+        return InitializationOptions(
             server_name=self.name,
             server_version=pkg_version("mcp"),
             capabilities=self.get_capabilities(
@@ -168,50 +172,16 @@ async def handler(_: Any):
         return decorator
 
     def get_prompt(self):
-        from mcp.types import (
-            GetPromptRequest,
-            GetPromptResult,
-            ImageContent,
-        )
-        from mcp.types import (
-            Role as Role,
-        )
-
         def decorator(
             func: Callable[
-                [str, dict[str, str] | None], Awaitable[types.PromptResponse]
+                [str, dict[str, str] | None], Awaitable[GetPromptResult]
             ],
         ):
             logger.debug("Registering handler for GetPromptRequest")
 
             async def handler(req: GetPromptRequest):
                 prompt_get = await func(req.params.name, req.params.arguments)
-                messages: list[PromptMessage] = []
-                for message in prompt_get.messages:
-                    match message.content:
-                        case str() as text_content:
-                            content = TextContent(type="text", text=text_content)
-                        case types.ImageContent() as img_content:
-                            content = ImageContent(
-                                type="image",
-                                data=img_content.data,
-                                mimeType=img_content.mime_type,
-                            )
-                        case types.EmbeddedResource() as resource:
-                            content = EmbeddedResource(
-                                type="resource", resource=resource.resource
-                            )
-                        case _:
-                            raise ValueError(
-                                f"Unexpected content type: {type(message.content)}"
-                            )
-
-                    prompt_message = PromptMessage(role=message.role, content=content)
-                    messages.append(prompt_message)
-
-                return ServerResult(
-                    GetPromptResult(description=prompt_get.desc, messages=messages)
-                )
+                return ServerResult(prompt_get)
 
             self.request_handlers[GetPromptRequest] = handler
             return func
@@ -338,7 +308,7 @@ def call_tool(self):
         def decorator(
             func: Callable[
                 ...,
-                Awaitable[Sequence[str | types.ImageContent | types.EmbeddedResource]],
+                Awaitable[Sequence[TextContent | ImageContent | EmbeddedResource]],
             ],
         ):
             logger.debug("Registering handler for CallToolRequest")
@@ -351,15 +321,15 @@ async def handler(req: CallToolRequest):
                         match result:
                             case str() as text:
                                 content.append(TextContent(type="text", text=text))
-                            case types.ImageContent() as img:
+                            case ImageContent() as img:
                                 content.append(
                                     ImageContent(
                                         type="image",
                                         data=img.data,
-                                        mimeType=img.mime_type,
+                                        mimeType=img.mimeType,
                                     )
                                 )
-                            case types.EmbeddedResource() as resource:
+                            case EmbeddedResource() as resource:
                                 content.append(
                                     EmbeddedResource(
                                         type="resource", resource=resource.resource
@@ -427,7 +397,7 @@ async def run(
         self,
         read_stream: MemoryObjectReceiveStream[JSONRPCMessage | Exception],
         write_stream: MemoryObjectSendStream[JSONRPCMessage],
-        initialization_options: types.InitializationOptions,
+        initialization_options: InitializationOptions,
         # When True, exceptions are returned as messages to the client.
         # When False, exceptions are raised, which will cause the server to shut down
         # but also make tracing exceptions much easier during testing and when using

src/mcp/server/__main__.py

@@ -6,7 +6,7 @@
 
 from mcp.server.session import ServerSession
 from mcp.server.stdio import stdio_server
-from mcp.server.types import InitializationOptions
+from mcp.server.models import InitializationOptions
 from mcp.types import ServerCapabilities
 
 if not sys.warnoptions:

src/mcp/server/models.py

@@ -0,0 +1,19 @@
+"""
+This module provides simpler types to use with the server for managing prompts
+and tools.
+"""
+
+from dataclasses import dataclass
+from typing import Literal
+
+from pydantic import BaseModel
+
+from mcp.types import (
+    ServerCapabilities,
+)
+
+
+class InitializationOptions(BaseModel):
+    server_name: str
+    server_version: str
+    capabilities: ServerCapabilities

src/mcp/server/session.py

@@ -6,7 +6,7 @@
 from anyio.streams.memory import MemoryObjectReceiveStream, MemoryObjectSendStream
 from pydantic import AnyUrl
 
-from mcp.server.types import InitializationOptions
+from mcp.server.models import InitializationOptions
 from mcp.shared.session import (
     BaseSession,
     RequestResponder,

src/mcp/server/types.py

@@ -2,7 +2,7 @@
 from pydantic import AnyUrl
 
 from mcp.server import Server
-from mcp.server.types import InitializationOptions
+from mcp.server.models import InitializationOptions
 from mcp.types import Resource, ServerCapabilities
 
 TEST_INITIALIZATION_OPTIONS = InitializationOptions(

tests/conftest.py

@@ -4,7 +4,7 @@
 from mcp.client.session import ClientSession
 from mcp.server import NotificationOptions, Server
 from mcp.server.session import ServerSession
-from mcp.server.types import InitializationOptions
+from mcp.server.models import InitializationOptions
 from mcp.types import (
     ClientNotification,
     InitializedNotification,