diff --git a/tools/registry.py b/tools/registry.py
index 9b6611fb4..354da7123 100644
--- a/tools/registry.py
+++ b/tools/registry.py
@@ -45,11 +45,20 @@ def _module_registers_tools(module_path: Path) -> bool:
 
     Only inspects module-body statements so that helper modules which happen
     to call ``registry.register()`` inside a function are not picked up.
+
+    A cheap text prefilter avoids the ``ast.parse`` cost for files that do not
+    mention both ``registry`` and ``register`` — a necessary condition for a
+    top-level ``registry.register()`` call to exist.
     """
     try:
         source = module_path.read_text(encoding="utf-8")
+    except OSError:
+        return False
+    if "registry" not in source or "register" not in source:
+        return False
+    try:
         tree = ast.parse(source, filename=str(module_path))
-    except (OSError, SyntaxError):
+    except SyntaxError:
         return False
 
     return any(_is_registry_register_call(stmt) for stmt in tree.body)