Merge pull request #705 from jlowin/object-functions

Deprecate passing functions to the server in favor of core objects

.github/workflows/run-tests.yml

@@ -47,4 +47,4 @@ jobs:
         run: uv sync --locked
 
       - name: Run tests
-        run: uv run pytest tests
+        run: uv run pytest tests -n auto

pyproject.toml

@@ -86,7 +86,7 @@ fallback-version = "0.0.0"
 asyncio_mode = "auto"
 asyncio_default_fixture_loop_scope = "session"
 asyncio_default_test_loop_scope = "session"
-filterwarnings = []
+# filterwarnings = ["error::DeprecationWarning"]
 timeout = 3
 env = [
     "FASTMCP_TEST_MODE=1",

src/fastmcp/contrib/mcp_mixin/mcp_mixin.py

@@ -3,6 +3,10 @@
 from collections.abc import Callable
 from typing import TYPE_CHECKING, Any
 
+from fastmcp.prompts.prompt import Prompt
+from fastmcp.resources.resource import Resource
+from fastmcp.tools.tool import Tool
+
 if TYPE_CHECKING:
     from fastmcp.server import FastMCP
 
@@ -128,7 +132,8 @@ class MCPMixin:
                 registration_info["name"] = (
                     f"{prefix}{separator}{registration_info['name']}"
                 )
-            mcp_server.add_tool(fn=method, **registration_info)
+            tool = Tool.from_function(fn=method, **registration_info)
+            mcp_server.add_tool(tool)
 
     def register_resources(
         self,
@@ -156,7 +161,8 @@ class MCPMixin:
                 registration_info["uri"] = (
                     f"{prefix}{separator}{registration_info['uri']}"
                 )
-            mcp_server.add_resource_fn(fn=method, **registration_info)
+            resource = Resource.from_function(fn=method, **registration_info)
+            mcp_server.add_resource(resource)
 
     def register_prompts(
         self,
@@ -180,7 +186,8 @@ class MCPMixin:
                 registration_info["name"] = (
                     f"{prefix}{separator}{registration_info['name']}"
                 )
-            mcp_server.add_prompt(fn=method, **registration_info)
+            prompt = Prompt.from_function(fn=method, **registration_info)
+            mcp_server.add_prompt(prompt)
 
     def register_all(
         self,

src/fastmcp/prompts/prompt_manager.py

@@ -1,7 +1,6 @@
-"""Prompt management functionality."""
-
 from __future__ import annotations as _annotations
 
+import warnings
 from collections.abc import Awaitable, Callable
 from typing import TYPE_CHECKING, Any
 
@@ -57,6 +56,11 @@ class PromptManager:
         tags: set[str] | None = None,
     ) -> FunctionPrompt:
         """Create a prompt from a function."""
+        # deprecated in 2.7.0
+        warnings.warn(
+            "PromptManager.add_prompt_from_fn() is deprecated. Use Prompt.from_function() and call add_prompt() instead.",
+            DeprecationWarning,
+        )
         prompt = FunctionPrompt.from_function(
             fn, name=name, description=description, tags=tags
         )

src/fastmcp/resources/resource_manager.py

@@ -1,6 +1,7 @@
 """Resource manager functionality."""
 
 import inspect
+import warnings
 from collections.abc import Callable
 from typing import Any
 
@@ -120,6 +121,11 @@ class ResourceManager:
             The added resource. If a resource with the same URI already exists,
             returns the existing resource.
         """
+        # deprecated in 2.7.0
+        warnings.warn(
+            "add_resource_from_fn is deprecated. Use Resource.from_function() and call add_resource() instead.",
+            DeprecationWarning,
+        )
         resource = Resource.from_function(
             fn=fn,
             uri=uri,
@@ -171,7 +177,11 @@ class ResourceManager:
         tags: set[str] | None = None,
     ) -> ResourceTemplate:
         """Create a template from a function."""
-
+        # deprecated in 2.7.0
+        warnings.warn(
+            "add_template_from_fn is deprecated. Use ResourceTemplate.from_function() and call add_template() instead.",
+            DeprecationWarning,
+        )
         template = ResourceTemplate.from_function(
             fn,
             uri_template=uri_template,

src/fastmcp/server/server.py

@@ -3,6 +3,7 @@
 from __future__ import annotations
 
 import datetime
+import inspect
 import re
 import warnings
 from collections.abc import AsyncIterator, Awaitable, Callable
@@ -44,7 +45,6 @@ import fastmcp.server
 import fastmcp.settings
 from fastmcp.exceptions import NotFoundError
 from fastmcp.prompts import Prompt, PromptManager
-from fastmcp.prompts.prompt import PromptResult
 from fastmcp.resources import Resource, ResourceManager
 from fastmcp.resources.template import ResourceTemplate
 from fastmcp.server.auth.auth import OAuthProvider
@@ -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
@@ -183,10 +183,9 @@ class FastMCP(Generic[LifespanResultT]):
 
         if tools:
             for tool in tools:
-                if isinstance(tool, Tool):
-                    self._tool_manager.add_tool(tool)
-                else:
-                    self.add_tool(tool)
+                if not isinstance(tool, Tool):
+                    tool = Tool.from_function(tool, serializer=self._tool_serializer)
+                self.add_tool(tool)
 
         # Set up MCP protocol handlers
         self._setup_handlers()
@@ -349,18 +348,18 @@ class FastMCP(Generic[LifespanResultT]):
         """
 
         def decorator(
-            func: Callable[[Request], Awaitable[Response]],
+            fn: Callable[[Request], Awaitable[Response]],
         ) -> Callable[[Request], Awaitable[Response]]:
             self._additional_http_routes.append(
                 Route(
                     path,
-                    endpoint=func,
+                    endpoint=fn,
                     methods=methods,
                     name=name,
                     include_in_schema=include_in_schema,
                 )
             )
-            return func
+            return fn
 
         return decorator
 
@@ -484,15 +483,7 @@ class FastMCP(Generic[LifespanResultT]):
 
             raise NotFoundError(f"Unknown prompt: {name}")
 
-    def add_tool(
-        self,
-        fn: AnyFunction,
-        name: str | None = None,
-        description: str | None = None,
-        tags: set[str] | None = None,
-        annotations: ToolAnnotations | dict[str, Any] | None = None,
-        exclude_args: list[str] | None = None,
-    ) -> None:
+    def add_tool(self, tool: Tool) -> None:
         """Add a tool to the server.
 
         The tool function can optionally request a Context object by adding a parameter
@@ -505,18 +496,6 @@ class FastMCP(Generic[LifespanResultT]):
             tags: Optional set of tags for categorizing the tool
             annotations: Optional annotations about the tool's behavior
         """
-        if isinstance(annotations, dict):
-            annotations = ToolAnnotations(**annotations)
-
-        tool = Tool.from_function(
-            fn,
-            name=name,
-            description=description,
-            tags=tags,
-            annotations=annotations,
-            exclude_args=exclude_args,
-        )
-
         self._tool_manager.add_tool(tool)
         self._cache.clear()
 
@@ -574,16 +553,20 @@ class FastMCP(Generic[LifespanResultT]):
                 "The @tool decorator was used incorrectly. "
                 "Did you forget to call it? Use @tool() instead of @tool"
             )
+        if isinstance(annotations, dict):
+            annotations = ToolAnnotations(**annotations)
 
         def decorator(fn: AnyFunction) -> AnyFunction:
-            self.add_tool(
+            tool = Tool.from_function(
                 fn,
                 name=name,
                 description=description,
                 tags=tags,
                 annotations=annotations,
                 exclude_args=exclude_args,
+                serializer=self._tool_serializer,
             )
+            self.add_tool(tool)
             return fn
 
         return decorator
@@ -598,6 +581,14 @@ class FastMCP(Generic[LifespanResultT]):
         self._resource_manager.add_resource(resource, key=key)
         self._cache.clear()
 
+    def add_template(self, template: ResourceTemplate, key: str | None = None) -> None:
+        """Add a resource template to the server.
+
+        Args:
+            template: A ResourceTemplate instance to add
+        """
+        self._resource_manager.add_template(template, key=key)
+
     def add_resource_fn(
         self,
         fn: AnyFunction,
@@ -620,6 +611,12 @@ class FastMCP(Generic[LifespanResultT]):
             mime_type: Optional MIME type for the resource
             tags: Optional set of tags for categorizing the resource
         """
+        # deprecated since 2.7.0
+        warnings.warn(
+            "The add_resource_fn method is deprecated. Use the resource decorator instead.",
+            DeprecationWarning,
+            stacklevel=2,
+        )
         self._resource_manager.add_resource_or_template_from_fn(
             fn=fn,
             uri=uri,
@@ -693,36 +690,54 @@ class FastMCP(Generic[LifespanResultT]):
             )
 
         def decorator(fn: AnyFunction) -> AnyFunction:
-            self.add_resource_fn(
-                fn=fn,
-                uri=uri,
-                name=name,
-                description=description,
-                mime_type=mime_type,
-                tags=tags,
+            from fastmcp.server.context import Context
+
+            # Check if this should be a template
+            has_uri_params = "{" in uri and "}" in uri
+            # check if the function has any parameters (other than injected context)
+            has_func_params = any(
+                p
+                for p in inspect.signature(fn).parameters.values()
+                if p.annotation is not Context
             )
+
+            if has_uri_params or has_func_params:
+                template = ResourceTemplate.from_function(
+                    fn=fn,
+                    uri_template=uri,
+                    name=name,
+                    description=description,
+                    mime_type=mime_type,
+                    tags=tags,
+                )
+                self.add_template(template)
+            elif not has_uri_params and not has_func_params:
+                resource = Resource.from_function(
+                    fn=fn,
+                    uri=uri,
+                    name=name,
+                    description=description,
+                    mime_type=mime_type,
+                    tags=tags,
+                )
+                self.add_resource(resource)
+            else:
+                raise ValueError(
+                    "Invalid resource or template definition due to a "
+                    "mismatch between URI parameters and function parameters."
+                )
+
             return fn
 
         return decorator
 
-    def add_prompt(
-        self,
-        fn: Callable[..., PromptResult | Awaitable[PromptResult]],
-        name: str | None = None,
-        description: str | None = None,
-        tags: set[str] | None = None,
-    ) -> None:
+    def add_prompt(self, prompt: Prompt) -> None:
         """Add a prompt to the server.
 
         Args:
             prompt: A Prompt instance to add
         """
-        self._prompt_manager.add_prompt_from_fn(
-            fn=fn,
-            name=name,
-            description=description,
-            tags=tags,
-        )
+        self._prompt_manager.add_prompt(prompt)
         self._cache.clear()
 
     def prompt(
@@ -787,9 +802,16 @@ class FastMCP(Generic[LifespanResultT]):
                 "Did you forget to call it? Use @prompt() instead of @prompt"
             )
 
-        def decorator(func: AnyFunction) -> AnyFunction:
-            self.add_prompt(func, name=name, description=description, tags=tags)
-            return DecoratedFunction(func)
+        def decorator(fn: AnyFunction) -> AnyFunction:
+            prompt = Prompt.from_function(
+                fn=fn,
+                name=name,
+                description=description,
+                tags=tags,
+            )
+
+            self.add_prompt(prompt)
+            return DecoratedFunction(fn)
 
         return decorator
 

src/fastmcp/tools/tool_manager.py

@@ -1,5 +1,6 @@
 from __future__ import annotations as _annotations
 
+import warnings
 from collections.abc import Callable
 from typing import TYPE_CHECKING, Any
 
@@ -22,11 +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
@@ -66,17 +65,23 @@ 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."""
+        # deprecated in 2.7.0
+        warnings.warn(
+            "ToolManager.add_tool_from_fn() is deprecated. Use Tool.from_function() and call add_tool() instead.",
+            DeprecationWarning,
+        )
         tool = Tool.from_function(
             fn,
             name=name,
             description=description,
             tags=tags,
             annotations=annotations,
-            serializer=self._serializer,
             exclude_args=exclude_args,
+            serializer=serializer,
         )
         return self.add_tool(tool)
 

tests/contrib/test_bulk_tool_caller.py

@@ -9,6 +9,7 @@ from fastmcp.contrib.bulk_tool_caller.bulk_tool_caller import (
     CallToolRequest,
     CallToolRequestResult,
 )
+from fastmcp.tools.tool import Tool
 
 ContentType = TextContent | ImageContent | EmbeddedResource
 
@@ -68,9 +69,9 @@ def no_return_tool_result_factory(arg1: str) -> CallToolRequestResult:
 def live_server_with_tool() -> FastMCP:
     """Fixture to create a FastMCP server instance with the echo_tool registered."""
     server = FastMCP()
-    server.add_tool(echo_tool)
-    server.add_tool(error_tool)
-    server.add_tool(no_return_tool)
+    server.add_tool(Tool.from_function(echo_tool))
+    server.add_tool(Tool.from_function(error_tool))
+    server.add_tool(Tool.from_function(no_return_tool))
     return server
 
 

tests/deprecated/__init__.py

@@ -0,0 +1,4 @@
+import pytest
+
+# reset deprecation warnings for this module
+pytestmark = pytest.mark.filterwarnings("default::DeprecationWarning")

tests/deprecated/test_deprecated.py

@@ -1,5 +1,3 @@
-"""Tests for deprecated functionality."""
-
 import warnings
 from unittest.mock import AsyncMock, patch
 
@@ -8,6 +6,9 @@ from starlette.applications import Starlette
 
 from fastmcp import Client, FastMCP
 
+# reset deprecation warnings for this module
+pytestmark = pytest.mark.filterwarnings("default::DeprecationWarning")
+
 
 def test_sse_app_deprecation_warning():
     """Test that sse_app raises a deprecation warning."""

tests/deprecated/test_mount_separators.py

@@ -4,6 +4,9 @@ import pytest
 
 from fastmcp import FastMCP
 
+# reset deprecation warnings for this module
+pytestmark = pytest.mark.filterwarnings("default::DeprecationWarning")
+
 
 def test_mount_tool_separator_deprecation_warning():
     """Test that using tool_separator in mount() raises a deprecation warning."""

tests/deprecated/test_resource_prefixes.py

@@ -1,5 +1,7 @@
 """Tests for legacy resource prefix behavior."""
 
+import pytest
+
 from fastmcp import Client, FastMCP
 from fastmcp.server.server import (
     add_resource_prefix,
@@ -8,6 +10,9 @@ from fastmcp.server.server import (
 )
 from fastmcp.utilities.tests import temporary_settings
 
+# reset deprecation warnings for this module
+pytestmark = pytest.mark.filterwarnings("default::DeprecationWarning")
+
 
 class TestLegacyResourcePrefixes:
     """Test the legacy resource prefix behavior."""

tests/deprecated/test_route_type_ignore.py

@@ -12,6 +12,9 @@ from fastmcp.server.openapi import (
     RouteType,
 )
 
+# reset deprecation warnings for this module
+pytestmark = pytest.mark.filterwarnings("default::DeprecationWarning")
+
 
 def test_route_type_ignore_deprecation_warning():
     """Test that using RouteType.IGNORE emits a deprecation warning."""

tests/server/test_import_server.py

@@ -3,7 +3,7 @@ from urllib.parse import quote
 
 from fastmcp.client.client import Client
 from fastmcp.server.server import FastMCP
-from fastmcp.tools.tool import FunctionTool
+from fastmcp.tools.tool import FunctionTool, Tool
 
 
 async def test_import_basic_functionality():
@@ -199,7 +199,7 @@ async def test_tool_custom_name_preserved_when_imported():
     def fetch_data(query: str) -> str:
         return f"Data for query: {query}"
 
-    api_app.add_tool(fetch_data, name="get_data")
+    api_app.add_tool(Tool.from_function(fetch_data, name="get_data"))
     await main_app.import_server("api", api_app)
 
     # Check that the tool is accessible by its prefixed name
@@ -219,7 +219,7 @@ async def test_call_imported_custom_named_tool():
     def fetch_data(query: str) -> str:
         return f"Data for query: {query}"
 
-    api_app.add_tool(fetch_data, name="get_data")
+    api_app.add_tool(Tool.from_function(fetch_data, name="get_data"))
     await main_app.import_server("api", api_app)
 
     async with Client(main_app) as client:
@@ -235,7 +235,7 @@ async def test_first_level_importing_with_custom_name():
     def calculate_value(input: int) -> int:
         return input * 2
 
-    provider_app.add_tool(calculate_value, name="compute")
+    provider_app.add_tool(Tool.from_function(calculate_value, name="compute"))
     await service_app.import_server("provider", provider_app)
 
     # Tool is accessible in the service app with the first prefix
@@ -254,7 +254,7 @@ async def test_nested_importing_preserves_prefixes():
     def calculate_value(input: int) -> int:
         return input * 2
 
-    provider_app.add_tool(calculate_value, name="compute")
+    provider_app.add_tool(Tool.from_function(calculate_value, name="compute"))
     await service_app.import_server("provider", provider_app)
     await main_app.import_server("service", service_app)
 
@@ -272,7 +272,7 @@ async def test_call_nested_imported_tool():
     def calculate_value(input: int) -> int:
         return input * 2
 
-    provider_app.add_tool(calculate_value, name="compute")
+    provider_app.add_tool(Tool.from_function(calculate_value, name="compute"))
     await service_app.import_server("provider", provider_app)
     await main_app.import_server("service", service_app)
 

tests/server/test_server.py

@@ -6,6 +6,8 @@ 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,
@@ -13,6 +15,7 @@ from fastmcp.server.server import (
     remove_resource_prefix,
 )
 from fastmcp.tools import FunctionTool
+from fastmcp.tools.tool import Tool
 
 
 class TestCreateServer:
@@ -173,7 +176,7 @@ class TestToolDecorator:
                 return self.x + y
 
         obj = MyClass(10)
-        mcp.add_tool(obj.add)
+        mcp.add_tool(Tool.from_function(obj.add))
         result = await mcp._mcp_call_tool("add", {"y": 2})
         assert result[0].text == "12"  # type: ignore[attr-defined]
 
@@ -187,7 +190,7 @@ class TestToolDecorator:
             def add(cls, y: int) -> int:
                 return cls.x + y
 
-        mcp.add_tool(MyClass.add)
+        mcp.add_tool(Tool.from_function(MyClass.add))
         result = await mcp._mcp_call_tool("add", {"y": 2})
         assert result[0].text == "12"  # type: ignore[attr-defined]
 
@@ -223,7 +226,7 @@ class TestToolDecorator:
             async def add(cls, y: int) -> int:
                 return cls.x + y
 
-        mcp.add_tool(MyClass.add)
+        mcp.add_tool(Tool.from_function(MyClass.add))
         result = await mcp._mcp_call_tool("add", {"y": 2})
         assert result[0].text == "12"  # type: ignore[attr-defined]
 
@@ -235,7 +238,7 @@ class TestToolDecorator:
             async def add(x: int, y: int) -> int:
                 return x + y
 
-        mcp.add_tool(MyClass.add)
+        mcp.add_tool(Tool.from_function(MyClass.add))
         result = await mcp._mcp_call_tool("add", {"x": 1, "y": 2})
         assert result[0].text == "3"  # type: ignore[attr-defined]
 
@@ -260,7 +263,7 @@ class TestToolDecorator:
             """Multiply two numbers."""
             return a * b
 
-        mcp.add_tool(multiply, name="custom_multiply")
+        mcp.add_tool(Tool.from_function(multiply, name="custom_multiply"))
 
         # Check that the tool is registered with the custom name
         tools = await mcp.get_tools()
@@ -386,8 +389,11 @@ class TestResourceDecorator:
                 return f"{self.prefix} Hello, world!"
 
         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:
@@ -404,8 +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:
@@ -505,9 +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")
@@ -523,11 +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")
@@ -678,7 +690,7 @@ class TestPromptDecorator:
                 return f"{self.prefix} Hello, world!"
 
         obj = MyClass("My prefix:")
-        mcp.add_prompt(obj.test_prompt, name="test_prompt")
+        mcp.add_prompt(Prompt.from_function(obj.test_prompt, name="test_prompt"))
 
         async with Client(mcp) as client:
             result = await client.get_prompt("test_prompt")
@@ -696,7 +708,7 @@ class TestPromptDecorator:
             def test_prompt(cls) -> str:
                 return f"{cls.prefix} Hello, world!"
 
-        mcp.add_prompt(MyClass.test_prompt, name="test_prompt")
+        mcp.add_prompt(Prompt.from_function(MyClass.test_prompt, name="test_prompt"))
 
         async with Client(mcp) as client:
             result = await client.get_prompt("test_prompt")

tests/server/test_server_interactions.py

@@ -19,9 +19,10 @@ from pydantic import AnyUrl, Field
 from fastmcp import Client, Context, FastMCP
 from fastmcp.client.transports import FastMCPTransport
 from fastmcp.exceptions import ToolError
-from fastmcp.prompts.prompt import EmbeddedResource, PromptMessage
-from fastmcp.resources import FileResource
+from fastmcp.prompts.prompt import EmbeddedResource, Prompt, PromptMessage
+from fastmcp.resources import FileResource, ResourceTemplate
 from fastmcp.resources.resource import FunctionResource
+from fastmcp.tools.tool import Tool
 from fastmcp.utilities.types import Image
 
 
@@ -691,7 +692,7 @@ class TestToolContextInjection:
             async def __call__(self, x: int, ctx: Context) -> int:
                 return x + int(ctx.request_id)
 
-        mcp.add_tool(MyTool())
+        mcp.add_tool(Tool.from_function(MyTool(), name="MyTool"))
 
         async with Client(mcp) as client:
             result = await client.call_tool("MyTool", {"x": 2})
@@ -1073,7 +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"))
@@ -1285,7 +1289,7 @@ class TestPromptContext:
             def __call__(self, name: str, ctx: Context) -> str:
                 return f"Hello, {name}! {ctx.request_id}"
 
-        mcp.add_prompt(MyPrompt(), name="my_prompt")
+        mcp.add_prompt(Prompt.from_function(MyPrompt(), name="my_prompt"))  # noqa: F821
 
         async with Client(mcp) as client:
             result = await client.get_prompt("my_prompt", {"name": "World"})

tests/server/test_tool_annotations.py

@@ -3,6 +3,7 @@ from typing import Any
 from mcp.types import ToolAnnotations
 
 from fastmcp import Client, FastMCP
+from fastmcp.tools.tool import Tool
 
 
 async def test_tool_annotations_in_tool_manager():
@@ -169,7 +170,7 @@ async def test_add_tool_method_annotations():
         """Create a new item."""
         return {"name": name, "value": value}
 
-    mcp.add_tool(
+    tool = Tool.from_function(
         create_item,
         name="create_item",
         annotations=ToolAnnotations(
@@ -179,6 +180,8 @@ async def test_add_tool_method_annotations():
         ),
     )
 
+    mcp.add_tool(tool)
+
     # Check internal tool objects directly
     tools = mcp._tool_manager.list_tools()
     assert len(tools) == 1
@@ -196,7 +199,7 @@ async def test_tool_functionality_with_annotations():
         """Create a new item."""
         return {"name": name, "value": value}
 
-    mcp.add_tool(
+    tool = Tool.from_function(
         create_item,
         name="create_item",
         annotations=ToolAnnotations(
@@ -205,6 +208,7 @@ async def test_tool_functionality_with_annotations():
             destructiveHint=False,
         ),
     )
+    mcp.add_tool(tool)
 
     # Use the tool to verify functionality is preserved
     async with Client(mcp) as client:

tests/server/test_tool_exclude_args.py

@@ -4,6 +4,7 @@ import pytest
 from mcp.types import TextContent
 
 from fastmcp import Client, FastMCP
+from fastmcp.tools.tool import Tool
 
 
 async def test_tool_exclude_args_in_tool_manager():
@@ -53,7 +54,12 @@ async def test_add_tool_method_exclude_args():
             pass
         return {"name": name, "value": value}
 
-    mcp.add_tool(create_item, name="create_item", exclude_args=["state"])
+    tool = Tool.from_function(
+        create_item,
+        name="create_item",
+        exclude_args=["state"],
+    )
+    mcp.add_tool(tool)
 
     # Check internal tool objects directly
     tools = mcp._tool_manager.list_tools()
@@ -77,7 +83,12 @@ async def test_tool_functionality_with_exclude_args():
             pass
         return {"name": name, "value": value}
 
-    mcp.add_tool(create_item, name="create_item", exclude_args=["state"])
+    tool = Tool.from_function(
+        create_item,
+        name="create_item",
+        exclude_args=["state"],
+    )
+    mcp.add_tool(tool)
 
     # Use the tool to verify functionality is preserved
     async with Client(mcp) as client:

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})