diff --git a/simple_typing_application/key_monitor/factory.py b/simple_typing_application/key_monitor/factory.py
index aaceb18..f538c1d 100644
--- a/simple_typing_application/key_monitor/factory.py
+++ b/simple_typing_application/key_monitor/factory.py
@@ -37,10 +37,11 @@ def create_key_monitor(
 
     # create key monitor
     logger.debug(f"create {key_monitor_cls.__name__}")
+    key_monitor_config: BaseKeyMonitorConfigModel
     if isinstance(config, key_monitor_config_model):
-        key_monitor_config: BaseKeyMonitorConfigModel = config
+        key_monitor_config = config
     else:
-        key_monitor_config: BaseKeyMonitorConfigModel = key_monitor_config_model(**config.model_dump())  # noqa
+        key_monitor_config = key_monitor_config_model(**config.model_dump())  # noqa
     key_monitor: BaseKeyMonitor = key_monitor_cls(**key_monitor_config.model_dump())  # type: ignore # noqa
 
     return key_monitor
diff --git a/simple_typing_application/sentence_generator/factory.py b/simple_typing_application/sentence_generator/factory.py
index 1cc92f9..5215f62 100644
--- a/simple_typing_application/sentence_generator/factory.py
+++ b/simple_typing_application/sentence_generator/factory.py
@@ -50,10 +50,11 @@ def create_sentence_generator(
 
     # create sentence generator
     logger.debug(f"create {sentence_generator_cls.__name__}")
+    sentence_generator_config: BaseSentenceGeneratorConfigModel
     if isinstance(config, sentence_generator_config_model):
-        sentence_generator_config: BaseSentenceGeneratorConfigModel = config
+        sentence_generator_config = config
     else:
-        sentence_generator_config: BaseSentenceGeneratorConfigModel = sentence_generator_config_model(**config.model_dump())  # noqa
+        sentence_generator_config = sentence_generator_config_model(**config.model_dump())  # noqa
     sentence_generator: BaseSentenceGenerator = sentence_generator_cls(**sentence_generator_config.model_dump())  # type: ignore # noqa
 
     return sentence_generator
diff --git a/simple_typing_application/sentence_generator/openai_sentence_generator.py b/simple_typing_application/sentence_generator/openai_sentence_generator.py
index 24663fb..015b3ba 100644
--- a/simple_typing_application/sentence_generator/openai_sentence_generator.py
+++ b/simple_typing_application/sentence_generator/openai_sentence_generator.py
@@ -90,8 +90,8 @@ async def generate(
         self._logger.debug(f"agent input messages: {messages}")
         with stopwatch(level=DEBUG, logger=self._logger, prefix="OpenAI agent invocation"):
             ret: dict[str, Any] = await self._agent.ainvoke(
-                {"messages": messages},
-            )  # type: ignore
+                {"messages": messages},  # type: ignore
+            )
         self._logger.debug(f"agent response: {ret}")
 
         # store to memory
diff --git a/simple_typing_application/ui/factory.py b/simple_typing_application/ui/factory.py
index 3f937af..f01f46d 100644
--- a/simple_typing_application/ui/factory.py
+++ b/simple_typing_application/ui/factory.py
@@ -32,10 +32,11 @@ def create_user_interface(
 
     # create user interface
     logger.debug(f"create {user_interface_cls.__name__}")
+    user_interface_config: BaseUserInterfaceConfigModel
     if isinstance(config, user_interface_config_model):
-        user_interface_config: BaseUserInterfaceConfigModel = config
+        user_interface_config = config
     else:
-        user_interface_config: BaseUserInterfaceConfigModel = user_interface_config_model(**config.model_dump())  # noqa
+        user_interface_config = user_interface_config_model(**config.model_dump())  # noqa
     user_interface: BaseUserInterface = user_interface_cls(**user_interface_config.model_dump())  # type: ignore # noqa
 
     return user_interface
diff --git a/simple_typing_application/utils/stopwatch.py b/simple_typing_application/utils/stopwatch.py
index 2dee7f4..c1f1ea5 100644
--- a/simple_typing_application/utils/stopwatch.py
+++ b/simple_typing_application/utils/stopwatch.py
@@ -3,7 +3,7 @@
 from contextlib import contextmanager
 from functools import wraps, partial
 from logging import Logger, getLogger
-from typing import Callable, Generator, TypeVar, ParamSpec
+from typing import Callable, Generator, TypeVar, ParamSpec, overload
 
 T = TypeVar("T")
 P = ParamSpec("P")
@@ -67,8 +67,9 @@ def stopwatch(
         log_func(log_msg_fmt.format(elapsed_time=end_time - start_time))
 
 
+@overload
 def stopwatch_deco(
-    func: Callable[P, T] | None = None,
+    func: Callable[P, T],
     *,
     level: int = logging.INFO,
     prefix: str | None = None,
@@ -77,9 +78,57 @@ def stopwatch_deco(
 ) -> Callable[P, T]:
     """Decorator to measure the execution time of a function.
 
+    Args:
+        func (Callable[P, T]): function to be decorated.
+        level (int, optional): log level. Defaults to logging.INFO.
+            Must be one of logging.DEBUG, logging.INFO, logging.WARNING, logging.ERROR, logging.CRITICAL.
+        prefix (str | None, optional): prefix of the log message. Defaults to None.
+        postfix (str, optional): postfix of the log message. Defaults to "".
+        logger (Logger, optional): logger. Defaults to logger.
+
+    Returns:
+        Callable[P, T]: decorated function.
+    """  # noqa
+    ...
+
+
+@overload
+def stopwatch_deco(
+    func: None = None,
+    *,
+    level: int = logging.INFO,
+    prefix: str | None = None,
+    postfix: str = "",
+    logger: Logger = logger,
+) -> Callable[[Callable[P, T]], Callable[P, T]]:
+    """Decorator to measure the execution time of a function.
+
+    Args:
+        func (None): Not used in this overload. This signature is for parameterized decoration (e.g., @stopwatch_deco(level=DEBUG)).
+        level (int, optional): log level. Defaults to logging.INFO.
+            Must be one of logging.DEBUG, logging.INFO, logging.WARNING, logging.ERROR, logging.CRITICAL.
+        prefix (str | None, optional): prefix of the log message. Defaults to None.
+        postfix (str, optional): postfix of the log message. Defaults to "".
+        logger (Logger, optional): logger. Defaults to logger.
+
+    Returns:
+        Callable[[Callable[P, T]], Callable[P, T]]: decorator.
+    """  # noqa
+    ...
+
+
+def stopwatch_deco(
+    func: Callable[P, T] | None = None,
+    *,
+    level: int = logging.INFO,
+    prefix: str | None = None,
+    postfix: str = "",
+    logger: Logger = logger,
+) -> Callable[P, T] | Callable[[Callable[P, T]], Callable[P, T]]:
+    """Decorator to measure the execution time of a function.
+
     Args:
         func (Callable[P, T], optional): function to be decorated. Defaults to None.
-        *,
         level (int, optional): log level. Defaults to logging.INFO.
             Must be one of logging.DEBUG, logging.INFO, logging.WARNING, logging.ERROR, logging.CRITICAL.
         prefix (str | None, optional): prefix of the log message. Defaults to None.