fix: validate tool kwargs even when empty to prevent cryptic TypeError (#4611)

lib/crewai/src/crewai/tools/base_tool.py

@@ -18,7 +18,6 @@ from pydantic import (
     BaseModel as PydanticBaseModel,
     ConfigDict,
     Field,
-    ValidationError,
     create_model,
     field_validator,
 )
@@ -163,7 +162,7 @@ class BaseTool(BaseModel, ABC):
         Raises:
             ValueError: If validation against args_schema fails.
         """
-        if kwargs and self.args_schema is not None and self.args_schema.model_fields:
+        if self.args_schema is not None and self.args_schema.model_fields:
             try:
                 validated = self.args_schema.model_validate(kwargs)
                 return validated.model_dump()
@@ -178,7 +177,8 @@ class BaseTool(BaseModel, ABC):
         *args: Any,
         **kwargs: Any,
     ) -> Any:
-        kwargs = self._validate_kwargs(kwargs)
+        if not args:
+            kwargs = self._validate_kwargs(kwargs)
 
         result = self._run(*args, **kwargs)
 
@@ -203,7 +203,8 @@ class BaseTool(BaseModel, ABC):
         Returns:
             The result of the tool execution.
         """
-        kwargs = self._validate_kwargs(kwargs)
+        if not args:
+            kwargs = self._validate_kwargs(kwargs)
         result = await self._arun(*args, **kwargs)
         self.current_usage_count += 1
         return result
@@ -356,7 +357,8 @@ class Tool(BaseTool, Generic[P, R]):
         Returns:
             The result of the tool execution.
         """
-        kwargs = self._validate_kwargs(kwargs)
+        if not args:
+            kwargs = self._validate_kwargs(kwargs)  # type: ignore[assignment]
 
         result = self.func(*args, **kwargs)
 
@@ -388,7 +390,8 @@ class Tool(BaseTool, Generic[P, R]):
         Returns:
             The result of the tool execution.
         """
-        kwargs = self._validate_kwargs(kwargs)
+        if not args:
+            kwargs = self._validate_kwargs(kwargs)  # type: ignore[assignment]
         result = await self._arun(*args, **kwargs)
         self.current_usage_count += 1
         return result

lib/crewai/tests/tools/test_base_tool.py

@@ -268,6 +268,13 @@ class TestBaseToolRunValidation:
         result = t.run(code="console.log('hi')", language="javascript")
         assert result == "Executed javascript: console.log('hi')"
 
+    def test_run_with_no_args_raises_validation_error(self) -> None:
+        """Calling run() with no arguments should raise a clear ValueError,
+        not a cryptic TypeError about missing positional arguments (GH-4611)."""
+        t = CodeExecutorTool()
+        with pytest.raises(ValueError, match="validation failed"):
+            t.run()
+
     def test_run_with_missing_required_kwarg_raises(self) -> None:
         """Missing required kwargs should raise ValueError from schema validation."""
         t = CodeExecutorTool()
@@ -378,6 +385,13 @@ class TestBaseToolArunValidation:
         result = await t.arun(code="print('hello')")
         assert result == "Async executed python: print('hello')"
 
+    @pytest.mark.asyncio
+    async def test_arun_with_no_args_raises_validation_error(self) -> None:
+        """Calling arun() with no arguments should raise a clear ValueError (GH-4611)."""
+        t = AsyncCodeExecutorTool()
+        with pytest.raises(ValueError, match="validation failed"):
+            await t.arun()
+
     @pytest.mark.asyncio
     async def test_arun_with_missing_required_kwarg_raises(self) -> None:
         """Missing required kwargs should raise ValueError in arun."""