chore: fix ruff linting issues in tools module

linting, args_schema default, and validator check

src/crewai/tools/base_tool.py

@@ -1,7 +1,8 @@
 import asyncio
 from abc import ABC, abstractmethod
+from collections.abc import Callable
 from inspect import signature
-from typing import Any, Callable, Type, get_args, get_origin, Optional, List
+from typing import Any, get_args, get_origin
 
 from pydantic import (
     BaseModel,
@@ -19,7 +20,7 @@ class EnvVar(BaseModel):
     name: str
     description: str
     required: bool = True
-    default: Optional[str] = None
+    default: str | None = None
 
 
 class BaseTool(BaseModel, ABC):
@@ -32,10 +33,10 @@ class BaseTool(BaseModel, ABC):
     """The unique name of the tool that clearly communicates its purpose."""
     description: str
     """Used to tell the model how/when/why to use the tool."""
-    env_vars: List[EnvVar] = []
+    env_vars: list[EnvVar] = []
     """List of environment variables used by the tool."""
-    args_schema: Type[PydanticBaseModel] = Field(
-        default_factory=_ArgsSchemaPlaceholder, validate_default=True
+    args_schema: type[PydanticBaseModel] = Field(
+        default=_ArgsSchemaPlaceholder, validate_default=True
     )
     """The schema for the arguments that the tool accepts."""
     description_updated: bool = False
@@ -52,9 +53,9 @@ class BaseTool(BaseModel, ABC):
     @field_validator("args_schema", mode="before")
     @classmethod
     def _default_args_schema(
-        cls, v: Type[PydanticBaseModel]
-    ) -> Type[PydanticBaseModel]:
-        if not isinstance(v, cls._ArgsSchemaPlaceholder):
+        cls, v: type[PydanticBaseModel]
+    ) -> type[PydanticBaseModel]:
+        if v != cls._ArgsSchemaPlaceholder:
             return v
 
         return type(
@@ -139,7 +140,7 @@ class BaseTool(BaseModel, ABC):
             # Infer args_schema from the function signature if not provided
             func_signature = signature(tool.func)
             annotations = func_signature.parameters
-            args_fields = {}
+            args_fields: dict[str, Any] = {}
             for name, param in annotations.items():
                 if name != "self":
                     param_annotation = (
@@ -247,7 +248,7 @@ class Tool(BaseTool):
             # Infer args_schema from the function signature if not provided
             func_signature = signature(tool.func)
             annotations = func_signature.parameters
-            args_fields = {}
+            args_fields: dict[str, Any] = {}
             for name, param in annotations.items():
                 if name != "self":
                     param_annotation = (