diff --git a/website/prebuild.py b/website/prebuild.py
index 0ca9d8f2002dd..b8b7e6231bbae 100755
--- a/website/prebuild.py
+++ b/website/prebuild.py
@@ -167,6 +167,7 @@ def next(nav_order: list[int]) -> int:
     label_subdir("docs/guides", next(nav_order))
     label_subdir("docs/project", next(nav_order), grandchild_dirs=True)
     label_subdir("docs/spec", next(nav_order))
+    # Provide a small file to cluster implementation-related directories.
     label_root_file(
         "implementation.md",
         "Implementation",