diff --git a/crystal_toolkit/helpers/utils.py b/crystal_toolkit/helpers/utils.py
index 4a8f75df..f19fb4d5 100644
--- a/crystal_toolkit/helpers/utils.py
+++ b/crystal_toolkit/helpers/utils.py
@@ -4,7 +4,7 @@
 import re
 import urllib.parse
 from fractions import Fraction
-from typing import TYPE_CHECKING, Any, Callable
+from typing import TYPE_CHECKING, Any, Callable, Literal
 from uuid import uuid4
 
 import dash
@@ -519,7 +519,7 @@ def hook_up_fig_with_struct_viewer(
     fig: go.Figure,
     df: pd.DataFrame,
     struct_col: str = "structure",
-    validate_id: Callable[[str], bool] = lambda id: True,
+    transform_id: Callable[[str], str | Literal[False]] = lambda mat_id: mat_id,
     highlight_selected: Callable[[dict[str, Any]], dict[str, Any]] | None = None,
 ) -> Dash:
     """Create a Dash app that hooks up a Plotly figure with a Crystal Toolkit structure
@@ -555,11 +555,10 @@ def hook_up_fig_with_struct_viewer(
         struct_col (str, optional): Name of the column in the data frame that contains
             the structures. Defaults to 'structure'. Can be instances of
             pymatgen.core.Structure or dicts created with Structure.as_dict().
-        validate_id (Callable[[str], bool], optional): Function that takes a string
+        transform_id (Callable[[str], str | False], optional): Function that takes a string
             extracted from the hovertext key of a hoverData event payload and returns
-            True if the string is a valid df row index. Defaults to lambda
-            id: True. Useful for not running the update-structure
-            callback on unexpected data.
+            a string that can be used to index the dataframe. Return False to prevent
+            the update-structure callback from being called.
         highlight_selected (Callable[[dict[str, Any]], dict[str, Any]], optional):
             Function that takes the clicked or last-hovered point and returns a dict of
             kwargs to be passed to go.Figure.add_annotation() to highlight said point.
@@ -642,9 +641,8 @@ def update_structure(
 
         # hover_data and click_data are identical since a hover event always precedes a
         # click so we always use hover_data
-        material_id = hover_data["points"][0]["hovertext"]
-        if not validate_id(material_id):
-            print(f"bad {material_id=}")
+        material_id = transform_id(hover_data["points"][0]["hovertext"])
+        if material_id is False:
             raise dash.exceptions.PreventUpdate
 
         struct = df[struct_col][material_id]