diff --git a/src/google/adk/tools/agent_tool.py b/src/google/adk/tools/agent_tool.py
index 6a1edcc6..7a8b15b5 100644
--- a/src/google/adk/tools/agent_tool.py
+++ b/src/google/adk/tools/agent_tool.py
@@ -18,8 +18,6 @@ from typing import Any
 from typing import TYPE_CHECKING
 
 from google.genai import types
-from pydantic import BaseModel
-from pydantic import ConfigDict
 from pydantic import model_validator
 from typing_extensions import override
 
@@ -164,8 +162,8 @@ class AgentTool(BaseTool):
       tool_result = merged_text
     return tool_result
 
-  @classmethod
   @override
+  @classmethod
   def from_config(
       cls, config: ToolArgsConfig, config_abs_path: str
   ) -> AgentTool:
diff --git a/src/google/adk/tools/base_tool.py b/src/google/adk/tools/base_tool.py
index 90c57539..c714fb11 100644
--- a/src/google/adk/tools/base_tool.py
+++ b/src/google/adk/tools/base_tool.py
@@ -30,7 +30,6 @@ from typing import Union
 
 from google.genai import types
 from pydantic import BaseModel
-from pydantic import ConfigDict
 
 from ..utils.variant_utils import get_google_llm_variant
 from ..utils.variant_utils import GoogleLLMVariant
@@ -40,6 +39,7 @@ logger = logging.getLogger("google_adk." + __name__)
 
 if TYPE_CHECKING:
   from ..models.llm_request import LlmRequest
+  from .tool_configs import ToolArgsConfig
 
 SelfTool = TypeVar("SelfTool", bound="BaseTool")
 
diff --git a/src/google/adk/utils/variant_utils.py b/src/google/adk/utils/variant_utils.py
index 0eef6163..5de82b42 100644
--- a/src/google/adk/utils/variant_utils.py
+++ b/src/google/adk/utils/variant_utils.py
@@ -39,7 +39,7 @@ class GoogleLLMVariant(Enum):
   """For using API Key from Google AI Studio"""
 
 
-def get_google_llm_variant() -> str:
+def get_google_llm_variant() -> GoogleLLMVariant:
   return (
       GoogleLLMVariant.VERTEX_AI
       if os.environ.get('GOOGLE_GENAI_USE_VERTEXAI', '0').lower()