chore: create union for working with message content (#939)

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

@@ -7,18 +7,16 @@ from typing import Any, Literal
 import pydantic_core
 from pydantic import BaseModel, Field, TypeAdapter, validate_call
 
-from mcp.types import AudioContent, EmbeddedResource, ImageContent, TextContent
-
-CONTENT_TYPES = TextContent | ImageContent | AudioContent | EmbeddedResource
+from mcp.types import Content, TextContent
 
 
 class Message(BaseModel):
     """Base class for all prompt messages."""
 
     role: Literal["user", "assistant"]
-    content: CONTENT_TYPES
+    content: Content
 
-    def __init__(self, content: str | CONTENT_TYPES, **kwargs: Any):
+    def __init__(self, content: str | Content, **kwargs: Any):
         if isinstance(content, str):
             content = TextContent(type="text", text=content)
         super().__init__(content=content, **kwargs)
@@ -29,7 +27,7 @@ class UserMessage(Message):
 
     role: Literal["user", "assistant"] = "user"
 
-    def __init__(self, content: str | CONTENT_TYPES, **kwargs: Any):
+    def __init__(self, content: str | Content, **kwargs: Any):
         super().__init__(content=content, **kwargs)
 
 
@@ -38,7 +36,7 @@ class AssistantMessage(Message):
 
     role: Literal["user", "assistant"] = "assistant"
 
-    def __init__(self, content: str | CONTENT_TYPES, **kwargs: Any):
+    def __init__(self, content: str | Content, **kwargs: Any):
         super().__init__(content=content, **kwargs)
 
 

src/mcp/server/fastmcp/server.py

@@ -52,10 +52,8 @@ from mcp.server.streamable_http_manager import StreamableHTTPSessionManager
 from mcp.shared.context import LifespanContextT, RequestContext, RequestT
 from mcp.types import (
     AnyFunction,
-    AudioContent,
-    EmbeddedResource,
+    Content,
     GetPromptResult,
-    ImageContent,
     TextContent,
     ToolAnnotations,
 )
@@ -256,9 +254,7 @@ class FastMCP:
             request_context = None
         return Context(request_context=request_context, fastmcp=self)
 
-    async def call_tool(
-        self, name: str, arguments: dict[str, Any]
-    ) -> Sequence[TextContent | ImageContent | AudioContent | EmbeddedResource]:
+    async def call_tool(self, name: str, arguments: dict[str, Any]) -> Sequence[Content]:
         """Call a tool by name with arguments."""
         context = self.get_context()
         result = await self._tool_manager.call_tool(name, arguments, context=context)
@@ -842,12 +838,12 @@ class FastMCP:
 
 def _convert_to_content(
     result: Any,
-) -> Sequence[TextContent | ImageContent | AudioContent | EmbeddedResource]:
+) -> Sequence[Content]:
     """Convert a result to a sequence of content objects."""
     if result is None:
         return []
 
-    if isinstance(result, TextContent | ImageContent | AudioContent | EmbeddedResource):
+    if isinstance(result, Content):
         return [result]
 
     if isinstance(result, Image):

src/mcp/server/lowlevel/server.py

@@ -384,9 +384,7 @@ class Server(Generic[LifespanResultT, RequestT]):
         def decorator(
             func: Callable[
                 ...,
-                Awaitable[
-                    Iterable[types.TextContent | types.ImageContent | types.AudioContent | types.EmbeddedResource]
-                ],
+                Awaitable[Iterable[types.Content]],
             ],
         ):
             logger.debug("Registering handler for CallToolRequest")