diff --git a/action.yml b/action.yml
index 53d65e85..5237f1a8 100644
--- a/action.yml
+++ b/action.yml
@@ -104,7 +104,7 @@ outputs:
   cache-hit:
     description: 'A boolean value to indicate an exact match was found for the primary key'
   cache-primary-key:
-    description: 'The primary cache key computed by the action for the configured build tool. Empty when caching is not enabled. Useful for composing with actions/cache or actions/cache/restore across jobs.'
+    description: 'The primary cache key computed by the action for the configured build tool. Empty when caching is not enabled or when caching is skipped (e.g. cache service unavailable). Useful for composing with actions/cache or actions/cache/restore across jobs.'
 runs:
   using: 'node24'
   main: 'dist/setup/index.js'