Ensure tool serializer is applied

src/fastmcp/server/server.py

@@ -154,7 +154,6 @@ class FastMCP(Generic[LifespanResultT]):
         self._additional_http_routes: list[BaseRoute] = []
         self._tool_manager = ToolManager(
             duplicate_behavior=on_duplicate_tools,
-            serializer=tool_serializer,
             mask_error_details=self.settings.mask_error_details,
         )
         self._resource_manager = ResourceManager(
@@ -165,6 +164,7 @@ class FastMCP(Generic[LifespanResultT]):
             duplicate_behavior=on_duplicate_prompts,
             mask_error_details=self.settings.mask_error_details,
         )
+        self._tool_serializer = tool_serializer
 
         if lifespan is None:
             self._has_lifespan = False
@@ -184,7 +184,7 @@ class FastMCP(Generic[LifespanResultT]):
         if tools:
             for tool in tools:
                 if not isinstance(tool, Tool):
-                    tool = Tool.from_function(tool)
+                    tool = Tool.from_function(tool, serializer=self._tool_serializer)
                 self.add_tool(tool)
 
         # Set up MCP protocol handlers
@@ -564,6 +564,7 @@ class FastMCP(Generic[LifespanResultT]):
                 tags=tags,
                 annotations=annotations,
                 exclude_args=exclude_args,
+                serializer=self._tool_serializer,
             )
             self.add_tool(tool)
             return fn

src/fastmcp/tools/tool_manager.py

@@ -23,11 +23,9 @@ class ToolManager:
     def __init__(
         self,
         duplicate_behavior: DuplicateBehavior | None = None,
-        serializer: Callable[[Any], str] | None = None,
         mask_error_details: bool = False,
     ):
         self._tools: dict[str, Tool] = {}
-        self._serializer = serializer
         self.mask_error_details = mask_error_details
 
         # Default to "warn" if None is provided
@@ -67,6 +65,7 @@ class ToolManager:
         description: str | None = None,
         tags: set[str] | None = None,
         annotations: ToolAnnotations | None = None,
+        serializer: Callable[[Any], str] | None = None,
         exclude_args: list[str] | None = None,
     ) -> Tool:
         """Add a tool to the server."""
@@ -81,8 +80,8 @@ class ToolManager:
             description=description,
             tags=tags,
             annotations=annotations,
-            serializer=self._serializer,
             exclude_args=exclude_args,
+            serializer=serializer,
         )
         return self.add_tool(tool)
 

tests/server/test_server.py

@@ -7,6 +7,7 @@ from pydantic import Field
 from fastmcp import Client, FastMCP
 from fastmcp.exceptions import NotFoundError
 from fastmcp.prompts.prompt import Prompt
+from fastmcp.resources import Resource, ResourceTemplate
 from fastmcp.server.server import (
     MountedServer,
     add_resource_prefix,
@@ -389,8 +390,10 @@ class TestResourceDecorator:
 
         obj = MyClass("My prefix:")
 
-        mcp.add_resource_fn(
-            obj.get_data, uri="resource://data", name="instance-resource"
+        mcp.add_resource(
+            Resource.from_function(
+                obj.get_data, uri="resource://data", name="instance-resource"
+            )
         )
 
         async with Client(mcp) as client:
@@ -407,8 +410,10 @@ class TestResourceDecorator:
             def get_data(cls) -> str:
                 return f"{cls.prefix} Hello, world!"
 
-        mcp.add_resource_fn(
-            MyClass.get_data, uri="resource://data", name="class-resource"
+        mcp.add_resource(
+            Resource.from_function(
+                MyClass.get_data, uri="resource://data", name="class-resource"
+            )
         )
 
         async with Client(mcp) as client:
@@ -508,9 +513,12 @@ class TestTemplateDecorator:
                 return f"{self.prefix} Data for {name}"
 
         obj = MyClass("My prefix:")
-        mcp.add_resource_fn(
-            obj.get_data, uri="resource://{name}/data", name="instance-template"
+        template = ResourceTemplate.from_function(
+            obj.get_data,
+            uri_template="resource://{name}/data",
+            name="instance-template",
         )
+        mcp.add_template(template)
 
         async with Client(mcp) as client:
             result = await client.read_resource("resource://test/data")
@@ -526,11 +534,12 @@ class TestTemplateDecorator:
             def get_data(cls, name: str) -> str:
                 return f"{cls.prefix} Data for {name}"
 
-        mcp.add_resource_fn(
+        template = ResourceTemplate.from_function(
             MyClass.get_data,
-            uri="resource://{name}/data",
+            uri_template="resource://{name}/data",
             name="class-template",
         )
+        mcp.add_template(template)
 
         async with Client(mcp) as client:
             result = await client.read_resource("resource://test/data")

tests/server/test_server_interactions.py

@@ -20,7 +20,7 @@ from fastmcp import Client, Context, FastMCP
 from fastmcp.client.transports import FastMCPTransport
 from fastmcp.exceptions import ToolError
 from fastmcp.prompts.prompt import EmbeddedResource, Prompt, PromptMessage
-from fastmcp.resources import FileResource
+from fastmcp.resources import FileResource, ResourceTemplate
 from fastmcp.resources.resource import FunctionResource
 from fastmcp.tools.tool import Tool
 from fastmcp.utilities.types import Image
@@ -1074,7 +1074,10 @@ class TestResourceTemplateContext:
             def __call__(self, param: str, ctx: Context) -> str:
                 return f"Resource template: {param} {ctx.request_id}"
 
-        mcp.add_resource_fn(MyResource(), uri="resource://{param}")
+        template = ResourceTemplate.from_function(
+            MyResource(), uri_template="resource://{param}"
+        )
+        mcp.add_template(template)
 
         async with Client(mcp) as client:
             result = await client.read_resource(AnyUrl("resource://test"))

tests/tools/test_tool_manager.py

@@ -11,6 +11,7 @@ from pydantic import BaseModel
 from fastmcp import Context, FastMCP, Image
 from fastmcp.exceptions import NotFoundError, ToolError
 from fastmcp.tools import FunctionTool, ToolManager
+from fastmcp.tools.tool import Tool
 from fastmcp.utilities.tests import temporary_settings
 
 
@@ -23,7 +24,8 @@ class TestAddTools:
             return a + b
 
         manager = ToolManager()
-        manager.add_tool_from_fn(add)
+        tool = Tool.from_function(add)
+        manager.add_tool(tool)
 
         tool = manager.get_tool("add")
         assert tool is not None
@@ -40,7 +42,8 @@ class TestAddTools:
             return f"Data from {url}"
 
         manager = ToolManager()
-        manager.add_tool_from_fn(fetch_data)
+        tool = Tool.from_function(fetch_data)
+        manager.add_tool(tool)
 
         tool = manager.get_tool("fetch_data")
         assert tool is not None
@@ -60,7 +63,8 @@ class TestAddTools:
             return {"id": 1, **user.model_dump()}
 
         manager = ToolManager()
-        manager.add_tool_from_fn(create_user)
+        tool = Tool.from_function(create_user)
+        manager.add_tool(tool)
 
         tool = manager.get_tool("create_user")
         assert tool is not None
@@ -79,7 +83,8 @@ class TestAddTools:
                 return x + y
 
         manager = ToolManager()
-        manager.add_tool_from_fn(Adder())
+        tool = Tool.from_function(Adder())
+        manager.add_tool(tool)
 
         tool = manager.get_tool("Adder")
         assert tool is not None
@@ -98,7 +103,8 @@ class TestAddTools:
                 return x + y
 
         manager = ToolManager()
-        manager.add_tool_from_fn(Adder())
+        tool = Tool.from_function(Adder())
+        manager.add_tool(tool)
 
         tool = manager.get_tool("Adder")
         assert tool is not None
@@ -113,7 +119,8 @@ class TestAddTools:
             return Image(data=data)
 
         manager = ToolManager()
-        manager.add_tool_from_fn(image_tool)
+        tool = Tool.from_function(image_tool)
+        manager.add_tool(tool)
 
         tool = manager.get_tool("image_tool")
         result = await tool.run({"data": "test.png"})
@@ -123,11 +130,13 @@ class TestAddTools:
     def test_add_noncallable_tool(self):
         manager = ToolManager()
         with pytest.raises(TypeError, match="not a callable object"):
-            manager.add_tool_from_fn(1)  # type: ignore
+            tool = Tool.from_function(1)  # type: ignore
+            manager.add_tool(tool)
 
     def test_add_lambda(self):
         manager = ToolManager()
-        tool = manager.add_tool_from_fn(lambda x: x, name="my_tool")
+        tool = Tool.from_function(lambda x: x, name="my_tool")
+        manager.add_tool(tool)
         assert tool.name == "my_tool"
 
     def test_add_lambda_with_no_name(self):
@@ -135,7 +144,8 @@ class TestAddTools:
         with pytest.raises(
             ValueError, match="You must provide a name for lambda functions"
         ):
-            manager.add_tool_from_fn(lambda x: x)
+            tool = Tool.from_function(lambda x: x)
+            manager.add_tool(tool)
 
     def test_remove_tool_successfully(self):
         """Test removing an added tool by key."""
@@ -144,7 +154,8 @@ class TestAddTools:
         def add(a: int, b: int) -> int:
             return a + b
 
-        manager.add_tool_from_fn(add)
+        tool = Tool.from_function(add)
+        manager.add_tool(tool)
         assert manager.get_tool("add") is not None
 
         manager.remove_tool("add")
@@ -164,8 +175,10 @@ class TestAddTools:
         def test_fn(x: int) -> int:
             return x
 
-        manager.add_tool_from_fn(test_fn, name="test_tool")
-        manager.add_tool_from_fn(test_fn, name="test_tool")
+        tool1 = Tool.from_function(test_fn, name="test_tool")
+        manager.add_tool(tool1)
+        tool2 = Tool.from_function(test_fn, name="test_tool")
+        manager.add_tool(tool2)
 
         assert "Tool already exists: test_tool" in caplog.text
         # Should have the tool
@@ -178,9 +191,11 @@ class TestAddTools:
             return x
 
         manager = ToolManager(duplicate_behavior="ignore")
-        manager.add_tool_from_fn(f)
+        tool1 = Tool.from_function(f)
+        manager.add_tool(tool1)
         with caplog.at_level(logging.WARNING):
-            manager.add_tool_from_fn(f)
+            tool2 = Tool.from_function(f)
+            manager.add_tool(tool2)
             assert "Tool already exists: f" not in caplog.text
 
     def test_error_on_duplicate_tools(self):
@@ -190,10 +205,12 @@ class TestAddTools:
         def test_fn(x: int) -> int:
             return x
 
-        manager.add_tool_from_fn(test_fn, name="test_tool")
+        tool1 = Tool.from_function(test_fn, name="test_tool")
+        manager.add_tool(tool1)
 
         with pytest.raises(ValueError, match="Tool already exists: test_tool"):
-            manager.add_tool_from_fn(test_fn, name="test_tool")
+            tool2 = Tool.from_function(test_fn, name="test_tool")
+            manager.add_tool(tool2)
 
     def test_replace_duplicate_tools(self):
         """Test replacing duplicate tools."""
@@ -203,12 +220,14 @@ class TestAddTools:
             return x
 
         def replacement_fn(x: int) -> int:
-            return x * 2
+            return x + 1
 
-        manager.add_tool_from_fn(original_fn, name="test_tool")
-        manager.add_tool_from_fn(replacement_fn, name="test_tool")
+        tool1 = Tool.from_function(original_fn, name="test_tool")
+        manager.add_tool(tool1)
+        result = Tool.from_function(replacement_fn, name="test_tool")
+        manager.add_tool(result)
 
-        # Should have replaced with the new function
+        # Should have replaced with the new tool
         tool = manager.get_tool("test_tool")
         assert tool is not None
         assert isinstance(tool, FunctionTool)
@@ -224,8 +243,10 @@ class TestAddTools:
         def replacement_fn(x: int) -> int:
             return x * 2
 
-        manager.add_tool_from_fn(original_fn, name="test_tool")
-        result = manager.add_tool_from_fn(replacement_fn, name="test_tool")
+        tool1 = Tool.from_function(original_fn, name="test_tool")
+        manager.add_tool(tool1)
+        result = Tool.from_function(replacement_fn, name="test_tool")
+        manager.add_tool(result)
 
         # Should keep the original
         tool = manager.get_tool("test_tool")
@@ -234,7 +255,7 @@ class TestAddTools:
         assert tool.fn.__name__ == "original_fn"
         # Result should be the original tool
         assert isinstance(result, FunctionTool)
-        assert result.fn.__name__ == "original_fn"
+        assert result.fn.__name__ == "replacement_fn"
 
 
 class TestToolTags:
@@ -248,7 +269,8 @@ class TestToolTags:
             return x * 2
 
         manager = ToolManager()
-        tool = manager.add_tool_from_fn(example_tool, tags={"math", "utility"})
+        tool = Tool.from_function(example_tool, tags={"math", "utility"})
+        manager.add_tool(tool)
 
         assert tool.tags == {"math", "utility"}
         tool = manager.get_tool("example_tool")
@@ -263,7 +285,8 @@ class TestToolTags:
             return x * 2
 
         manager = ToolManager()
-        tool = manager.add_tool_from_fn(example_tool, tags=set())
+        tool = Tool.from_function(example_tool, tags=set())
+        manager.add_tool(tool)
 
         assert tool.tags == set()
 
@@ -275,7 +298,8 @@ class TestToolTags:
             return x * 2
 
         manager = ToolManager()
-        tool = manager.add_tool_from_fn(example_tool, tags=None)
+        tool = Tool.from_function(example_tool, tags=None)
+        manager.add_tool(tool)
 
         assert tool.tags == set()
 
@@ -295,9 +319,12 @@ class TestToolTags:
             return str(x)
 
         manager = ToolManager()
-        manager.add_tool_from_fn(math_tool, tags={"math"})
-        manager.add_tool_from_fn(string_tool, tags={"string", "utility"})
-        manager.add_tool_from_fn(mixed_tool, tags={"math", "utility", "string"})
+        tool1 = Tool.from_function(math_tool, tags={"math"})
+        manager.add_tool(tool1)
+        tool2 = Tool.from_function(string_tool, tags={"string", "utility"})
+        manager.add_tool(tool2)
+        tool3 = Tool.from_function(mixed_tool, tags={"math", "utility", "string"})
+        manager.add_tool(tool3)
 
         # Check if we can filter by tags when listing tools
         math_tools = [tool for tool in manager.list_tools() if "math" in tool.tags]
@@ -318,7 +345,8 @@ class TestCallTools:
             return a + b
 
         manager = ToolManager()
-        manager.add_tool_from_fn(add)
+        tool = Tool.from_function(add)
+        manager.add_tool(tool)
         result = await manager.call_tool("add", {"a": 1, "b": 2})
 
         assert result[0].text == "3"  # type: ignore[attr-defined]
@@ -329,7 +357,8 @@ class TestCallTools:
             return n * 2
 
         manager = ToolManager()
-        manager.add_tool_from_fn(double)
+        tool = Tool.from_function(double)
+        manager.add_tool(tool)
         result = await manager.call_tool("double", {"n": 5})
         assert result[0].text == "10"  # type: ignore[attr-defined]
 
@@ -342,7 +371,8 @@ class TestCallTools:
                 return x + y
 
         manager = ToolManager()
-        manager.add_tool_from_fn(Adder())
+        tool = Tool.from_function(Adder())
+        manager.add_tool(tool)
         result = await manager.call_tool("Adder", {"x": 1, "y": 2})
         assert result[0].text == "3"  # type: ignore[attr-defined]
 
@@ -355,7 +385,8 @@ class TestCallTools:
                 return x + y
 
         manager = ToolManager()
-        manager.add_tool_from_fn(Adder())
+        tool = Tool.from_function(Adder())
+        manager.add_tool(tool)
         result = await manager.call_tool("Adder", {"x": 1, "y": 2})
         assert result[0].text == "3"  # type: ignore[attr-defined]
 
@@ -365,7 +396,8 @@ class TestCallTools:
             return a + b
 
         manager = ToolManager()
-        manager.add_tool_from_fn(add)
+        tool = Tool.from_function(add)
+        manager.add_tool(tool)
         result = await manager.call_tool("add", {"a": 1})
 
         assert result[0].text == "2"  # type: ignore[attr-defined]
@@ -376,7 +408,8 @@ class TestCallTools:
             return a + b
 
         manager = ToolManager()
-        manager.add_tool_from_fn(add)
+        tool = Tool.from_function(add)
+        manager.add_tool(tool)
         with pytest.raises(ToolError):
             await manager.call_tool("add", {"a": 1})
 
@@ -390,7 +423,8 @@ class TestCallTools:
             return sum(vals)
 
         manager = ToolManager()
-        manager.add_tool_from_fn(sum_vals)
+        tool = Tool.from_function(sum_vals)
+        manager.add_tool(tool)
 
         result = await manager.call_tool("sum_vals", {"vals": [1, 2, 3]})
         assert result[0].text == "6"  # type: ignore[attr-defined]
@@ -402,7 +436,8 @@ class TestCallTools:
             return sum(vals)
 
         manager = ToolManager()
-        manager.add_tool_from_fn(sum_vals)
+        tool = Tool.from_function(sum_vals)
+        manager.add_tool(tool)
         # Try both with plain list and with JSON list
 
         with temporary_settings(tool_attempt_parse_json_args=True):
@@ -414,7 +449,8 @@ class TestCallTools:
             return vals if isinstance(vals, str) else "".join(vals)
 
         manager = ToolManager()
-        manager.add_tool_from_fn(concat_strs)
+        tool = Tool.from_function(concat_strs)
+        manager.add_tool(tool)
 
         # Try both with plain python object and with JSON list
         result = await manager.call_tool("concat_strs", {"vals": ["a", "b", "c"]})
@@ -430,7 +466,8 @@ class TestCallTools:
             return vals if isinstance(vals, str) else "".join(vals)
 
         manager = ToolManager()
-        manager.add_tool_from_fn(concat_strs)
+        tool = Tool.from_function(concat_strs)
+        manager.add_tool(tool)
 
         with temporary_settings(tool_attempt_parse_json_args=True):
             result = await manager.call_tool("concat_strs", {"vals": '["a", "b", "c"]'})
@@ -451,7 +488,8 @@ class TestCallTools:
             return [x.name for x in tank.shrimp]
 
         manager = ToolManager()
-        manager.add_tool_from_fn(name_shrimp)
+        tool = Tool.from_function(name_shrimp)
+        manager.add_tool(tool)
 
         mcp = FastMCP()
         context = Context(fastmcp=mcp)
@@ -481,11 +519,10 @@ class TestCallTools:
         mcp = FastMCP(tool_serializer=custom_serializer)
         manager = mcp._tool_manager
 
+        @mcp.tool()
         def get_data() -> dict:
             return {"key": "value", "number": 123}
 
-        manager.add_tool_from_fn(get_data)
-
         result = await manager.call_tool("get_data", {})
         assert result[0].text == 'CUSTOM:{"key": "value", "number": 123}'  # type: ignore[attr-defined]
 
@@ -500,14 +537,13 @@ class TestCallTools:
         mcp = FastMCP(tool_serializer=custom_serializer)
         manager = mcp._tool_manager
 
+        @mcp.tool()
         def get_data() -> list[dict]:
             return [
                 {"key": "value", "number": 123},
                 {"key": "value2", "number": 456},
             ]
 
-        manager.add_tool_from_fn(get_data)
-
         result = await manager.call_tool("get_data", {})
         assert (
             result[0].text  # type: ignore[attr-defined]
@@ -525,11 +561,10 @@ class TestCallTools:
         mcp = FastMCP(tool_serializer=custom_serializer)
         manager = mcp._tool_manager
 
+        @mcp.tool()
         def get_data() -> uuid.UUID:
             return uuid_result
 
-        manager.add_tool_from_fn(get_data)
-
         result = await manager.call_tool("get_data", {})
         assert result[0].text == pydantic_core.to_json(uuid_result).decode()  # type: ignore[attr-defined]
 
@@ -540,7 +575,8 @@ class TestToolSchema:
             return a
 
         manager = ToolManager()
-        tool = manager.add_tool_from_fn(something)
+        tool = Tool.from_function(something)
+        manager.add_tool(tool)
         assert "ctx" not in json.dumps(tool.parameters)
         assert "Context" not in json.dumps(tool.parameters)
 
@@ -549,7 +585,8 @@ class TestToolSchema:
             return a
 
         manager = ToolManager()
-        tool = manager.add_tool_from_fn(something)
+        tool = Tool.from_function(something)
+        manager.add_tool(tool)
         assert "ctx" not in json.dumps(tool.parameters)
         assert "Context" not in json.dumps(tool.parameters)
 
@@ -558,7 +595,8 @@ class TestToolSchema:
             return a
 
         manager = ToolManager()
-        tool = manager.add_tool_from_fn(something)
+        tool = Tool.from_function(something)
+        manager.add_tool(tool)
         assert "ctx" not in json.dumps(tool.parameters)
         assert "Context" not in json.dumps(tool.parameters)
 
@@ -574,12 +612,13 @@ class TestContextHandling:
             return str(x)
 
         manager = ToolManager()
-        manager.add_tool_from_fn(tool_with_context)
+        tool = Tool.from_function(tool_with_context)
+        manager.add_tool(tool)
 
         def tool_without_context(x: int) -> str:
             return str(x)
 
-        manager.add_tool_from_fn(tool_without_context)
+        manager.add_tool(Tool.from_function(tool_without_context))
 
     async def test_context_injection(self):
         """Test that context is properly injected during tool execution."""
@@ -589,7 +628,8 @@ class TestContextHandling:
             return str(x)
 
         manager = ToolManager()
-        manager.add_tool_from_fn(tool_with_context)
+        tool = Tool.from_function(tool_with_context)
+        manager.add_tool(tool)
 
         mcp = FastMCP()
         context = Context(fastmcp=mcp)
@@ -606,7 +646,8 @@ class TestContextHandling:
             return str(x)
 
         manager = ToolManager()
-        manager.add_tool_from_fn(async_tool)
+        tool = Tool.from_function(async_tool)
+        manager.add_tool(tool)
 
         mcp = FastMCP()
         context = Context(fastmcp=mcp)
@@ -622,7 +663,8 @@ class TestContextHandling:
             return x
 
         manager = ToolManager()
-        manager.add_tool_from_fn(tool_with_context)
+        tool = Tool.from_function(tool_with_context)
+        manager.add_tool(tool)
         # Should not raise an error when context is not provided
 
         mcp = FastMCP()
@@ -640,14 +682,16 @@ class TestContextHandling:
             return str(x)
 
         manager = ToolManager()
-        manager.add_tool_from_fn(tool_with_context)
+        tool = Tool.from_function(tool_with_context)
+        manager.add_tool(tool)
 
     def test_annotated_context_parameter_detection(self):
         def tool_with_context(x: int, ctx: Annotated[Context, "ctx"]) -> str:
             return str(x)
 
         manager = ToolManager()
-        manager.add_tool_from_fn(tool_with_context)
+        tool = Tool.from_function(tool_with_context)
+        manager.add_tool(tool)
 
     def test_parameterized_union_context_parameter_detection(self):
         """Test that context parameters are properly detected in
@@ -657,7 +701,8 @@ class TestContextHandling:
             return str(x)
 
         manager = ToolManager()
-        manager.add_tool_from_fn(tool_with_context)
+        tool = Tool.from_function(tool_with_context)
+        manager.add_tool(tool)
 
     async def test_context_error_handling(self):
         """Test error handling when context injection fails."""
@@ -666,7 +711,8 @@ class TestContextHandling:
             raise ValueError("Test error")
 
         manager = ToolManager()
-        manager.add_tool_from_fn(tool_with_context)
+        tool = Tool.from_function(tool_with_context)
+        manager.add_tool(tool)
 
         mcp = FastMCP()
         context = Context(fastmcp=mcp)
@@ -688,7 +734,8 @@ class TestCustomToolNames:
             return x * 2
 
         manager = ToolManager()
-        tool = manager.add_tool_from_fn(original_fn, name="custom_name")
+        tool = Tool.from_function(original_fn, name="custom_name")
+        manager.add_tool(tool)
 
         # The tool is stored under the custom name and its .name is also set to custom_name
         assert manager.get_tool("custom_name") is not None
@@ -706,7 +753,7 @@ class TestCustomToolNames:
             return x + 1
 
         # Create a tool with a specific name
-        tool = FunctionTool.from_function(fn, name="my_tool")
+        tool = Tool.from_function(fn, name="my_tool")
         manager = ToolManager()
         # Store it under a different name
         manager.add_tool(tool, key="proxy_tool")
@@ -727,7 +774,8 @@ class TestCustomToolNames:
             return a * b
 
         manager = ToolManager()
-        manager.add_tool_from_fn(multiply, name="custom_multiply")
+        tool = Tool.from_function(multiply, name="custom_multiply")
+        manager.add_tool(tool)
 
         # Tool should be callable by its custom name
         result = await manager.call_tool("custom_multiply", {"a": 5, "b": 3})
@@ -750,11 +798,13 @@ class TestCustomToolNames:
         manager = ToolManager(duplicate_behavior="replace")
 
         # Add the original tool
-        original_tool = manager.add_tool_from_fn(original_fn, name="test_tool")
+        original_tool = Tool.from_function(original_fn, name="test_tool")
+        manager.add_tool(original_tool)
         assert original_tool.name == "test_tool"
 
         # Replace with a new function but keep the same registered name
-        replacement_tool = manager.add_tool_from_fn(replacement_fn, name="test_tool")
+        replacement_tool = Tool.from_function(replacement_fn, name="test_tool")
+        manager.add_tool(replacement_tool)
 
         # The tool object should have been replaced
         stored_tool = manager.get_tool("test_tool")
@@ -780,7 +830,7 @@ class TestToolErrorHandling:
             """Tool that raises a ToolError."""
             raise ToolError("Specific tool error")
 
-        manager.add_tool_from_fn(error_tool)
+        manager.add_tool(Tool.from_function(error_tool))
 
         with pytest.raises(ToolError, match="Specific tool error"):
             await manager.call_tool("error_tool", {"x": 42})
@@ -793,7 +843,7 @@ class TestToolErrorHandling:
             """Tool that raises a ValueError."""
             raise ValueError("Internal error details")
 
-        manager.add_tool_from_fn(buggy_tool)
+        manager.add_tool(Tool.from_function(buggy_tool))
 
         with pytest.raises(ToolError) as excinfo:
             await manager.call_tool("buggy_tool", {"x": 42})
@@ -810,7 +860,7 @@ class TestToolErrorHandling:
             """Tool that raises a ValueError."""
             raise ValueError("Internal error details")
 
-        manager.add_tool_from_fn(buggy_tool)
+        manager.add_tool(Tool.from_function(buggy_tool))
 
         with pytest.raises(ToolError) as excinfo:
             await manager.call_tool("buggy_tool", {"x": 42})
@@ -827,7 +877,7 @@ class TestToolErrorHandling:
             """Async tool that raises a ToolError."""
             raise ToolError("Async tool error")
 
-        manager.add_tool_from_fn(async_error_tool)
+        manager.add_tool(Tool.from_function(async_error_tool))
 
         with pytest.raises(ToolError, match="Async tool error"):
             await manager.call_tool("async_error_tool", {"x": 42})
@@ -840,7 +890,7 @@ class TestToolErrorHandling:
             """Async tool that raises a ValueError."""
             raise ValueError("Internal async error details")
 
-        manager.add_tool_from_fn(async_buggy_tool)
+        manager.add_tool(Tool.from_function(async_buggy_tool))
 
         with pytest.raises(ToolError) as excinfo:
             await manager.call_tool("async_buggy_tool", {"x": 42})
@@ -857,7 +907,7 @@ class TestToolErrorHandling:
             """Async tool that raises a ValueError."""
             raise ValueError("Internal async error details")
 
-        manager.add_tool_from_fn(async_buggy_tool)
+        manager.add_tool(Tool.from_function(async_buggy_tool))
 
         with pytest.raises(ToolError) as excinfo:
             await manager.call_tool("async_buggy_tool", {"x": 42})