Decorators return functions instead of component objects (#2856)

tests/server/middleware/test_caching.py

@@ -21,7 +21,8 @@ from pydantic import AnyUrl, BaseModel
 from fastmcp import Context, FastMCP
 from fastmcp.client.client import CallToolResult, Client
 from fastmcp.client.transports import FastMCPTransport
-from fastmcp.prompts.prompt import FunctionPrompt, Message, Prompt
+from fastmcp.prompts.function_prompt import FunctionPrompt
+from fastmcp.prompts.prompt import Message, Prompt
 from fastmcp.resources.resource import Resource
 from fastmcp.server.middleware.caching import (
     CachableToolResult,

tests/server/middleware/test_tool_injection.py

@@ -16,7 +16,8 @@ from fastmcp.server.middleware.tool_injection import (
     ResourceToolMiddleware,
     ToolInjectionMiddleware,
 )
-from fastmcp.tools.tool import FunctionTool, Tool
+from fastmcp.tools.function_tool import FunctionTool
+from fastmcp.tools.tool import Tool
 
 
 def multiply_fn(a: int, b: int) -> int:

tests/server/providers/test_local_provider_prompts.py

@@ -10,7 +10,7 @@ from mcp.types import TextContent
 
 from fastmcp import Client, Context, FastMCP
 from fastmcp.exceptions import NotFoundError
-from fastmcp.prompts.prompt import FunctionPrompt, Prompt
+from fastmcp.prompts.prompt import Prompt
 
 
 class TestPromptContext:
@@ -247,6 +247,10 @@ class TestPromptDecorator:
 
     async def test_prompt_direct_function_call(self):
         """Test that prompts can be registered via direct function call."""
+        from typing import cast
+
+        from fastmcp.prompts.function_prompt import DecoratedPrompt
+
         mcp = FastMCP()
 
         def standalone_function() -> str:
@@ -255,11 +259,16 @@ class TestPromptDecorator:
 
         result_fn = mcp.prompt(standalone_function, name="direct_call_prompt")
 
-        assert isinstance(result_fn, FunctionPrompt)
+        # In new decorator mode, returns the function with metadata
+        decorated = cast(DecoratedPrompt, result_fn)
+        assert hasattr(result_fn, "__fastmcp__")
+        assert decorated.__fastmcp__.name == "direct_call_prompt"
+        assert result_fn is standalone_function
 
         prompts = await mcp.get_prompts()
         prompt = next(p for p in prompts if p.name == "direct_call_prompt")
-        assert prompt is result_fn
+        # Prompt is registered separately, not same object as decorated function
+        assert prompt.name == "direct_call_prompt"
 
         result = await mcp.render_prompt("direct_call_prompt")
         assert len(result.messages) == 1

tests/server/providers/test_local_provider_tools.py

@@ -793,6 +793,10 @@ class TestToolOutputSchema:
         assert result.structured_content is None
 
     async def test_manual_structured_content(self):
+        from typing import cast
+
+        from fastmcp.tools.function_tool import DecoratedTool
+
         mcp = FastMCP()
 
         @mcp.tool
@@ -801,7 +805,12 @@ class TestToolOutputSchema:
                 content="Hello, world!", structured_content={"message": "Hello, world!"}
             )
 
-        assert f.output_schema is None
+        # In new decorator mode, check metadata instead of attributes
+        from fastmcp.utilities.types import NotSet
+
+        decorated = cast(DecoratedTool, f)
+        assert hasattr(f, "__fastmcp__")
+        assert decorated.__fastmcp__.output_schema is NotSet
 
         result = await mcp.call_tool("f", {})
         assert isinstance(result.content, list)
@@ -1312,7 +1321,9 @@ class TestToolDecorator:
 
     async def test_tool_direct_function_call(self):
         """Test that tools can be registered via direct function call."""
-        from fastmcp.tools import FunctionTool
+        from typing import cast
+
+        from fastmcp.tools.function_tool import DecoratedTool
 
         mcp = FastMCP()
 
@@ -1322,11 +1333,16 @@ class TestToolDecorator:
 
         result_fn = mcp.tool(standalone_function, name="direct_call_tool")
 
-        assert isinstance(result_fn, FunctionTool)
+        # In new decorator mode, returns the function with metadata
+        decorated = cast(DecoratedTool, result_fn)
+        assert hasattr(result_fn, "__fastmcp__")
+        assert decorated.__fastmcp__.name == "direct_call_tool"
+        assert result_fn is standalone_function
 
         tools = await mcp.get_tools()
         tool = next(t for t in tools if t.name == "direct_call_tool")
-        assert tool is result_fn
+        # Tool is registered separately, not same object as decorated function
+        assert tool.name == "direct_call_tool"
 
         result = await mcp.call_tool("direct_call_tool", {"x": 5, "y": 3})
         assert result.structured_content == {"result": 8}

tests/server/tasks/test_sync_function_task_disabled.py

@@ -8,9 +8,9 @@ ValueError when task=True is used with a sync function.
 import pytest
 
 from fastmcp import FastMCP
-from fastmcp.prompts.prompt import FunctionPrompt
-from fastmcp.resources.resource import FunctionResource
-from fastmcp.tools.tool import FunctionTool
+from fastmcp.prompts.function_prompt import FunctionPrompt
+from fastmcp.resources.function_resource import FunctionResource
+from fastmcp.tools.function_tool import FunctionTool
 
 
 async def test_sync_tool_with_explicit_task_true_raises():

tests/server/test_providers.py

@@ -7,8 +7,10 @@ import pytest
 from mcp.types import AnyUrl, TextContent
 
 from fastmcp import FastMCP
-from fastmcp.prompts.prompt import FunctionPrompt, Prompt
-from fastmcp.resources.resource import FunctionResource, Resource
+from fastmcp.prompts.function_prompt import FunctionPrompt
+from fastmcp.prompts.prompt import Prompt
+from fastmcp.resources.function_resource import FunctionResource
+from fastmcp.resources.resource import Resource
 from fastmcp.resources.template import FunctionResourceTemplate, ResourceTemplate
 from fastmcp.server.providers import Provider
 from fastmcp.tools.tool import Tool, ToolResult