diff --git a/masque/builder/tools.py b/masque/builder/tools.py
index 148af4d..0e08674 100644
--- a/masque/builder/tools.py
+++ b/masque/builder/tools.py
@@ -3,7 +3,7 @@ Tools are objects which dynamically generate simple single-use devices (e.g. wir
 
 # TODO document all tools
 """
-from typing import Literal, Any, Self
+from typing import Literal, Any, Self, cast, TYPE_CHECKING
 from collections.abc import Sequence, Callable
 from abc import ABCMeta  # , abstractmethod     # TODO any way to make Tool ok with implementing only one method?
 from dataclasses import dataclass