diff --git a/polymind/core/tool.py b/polymind/core/tool.py
index 25bc6f6..9047b47 100644
--- a/polymind/core/tool.py
+++ b/polymind/core/tool.py
@@ -96,7 +96,7 @@ def check_type(cls, v: str) -> str:
         )
 
 
-class AbstractTool(BaseModel, ABC):
+class AbstractTool(BaseModel):
     """The base class of the tool.
     In an agent system, a tool is an object that can be used to perform a task.
     For example, search for information from the internet, query a database,
@@ -258,7 +258,7 @@ def _validate_output_message(self, output_message: Message) -> None:
                     )
 
 
-class BaseTool(AbstractTool):
+class BaseTool(AbstractTool, ABC):
     async def __call__(self, input: Message) -> Message:
         self._validate_input_message(input)
         output_message = await self._execute(input)