diff --git a/backend/app/main.py b/backend/app/main.py
index 9a95801e74..bb88669f87 100644
--- a/backend/app/main.py
+++ b/backend/app/main.py
@@ -8,6 +8,11 @@
 
 
 def custom_generate_unique_id(route: APIRoute) -> str:
+    if not route.tags:
+        raise ValueError(
+            f"Route '{route.name}' is missing a tag. Each route "
+            "must have at least one tag for client generation."
+        )
     return f"{route.tags[0]}-{route.name}"