diff --git a/lib/tools/smart-home.ts b/lib/tools/smart-home.ts
index c2b609f..aca3066 100644
--- a/lib/tools/smart-home.ts
+++ b/lib/tools/smart-home.ts
@@ -69,7 +69,7 @@ const controlAirPurifier: VoiceTool = {
         preset_mode: mode,
       }
     } else {
-      return { error:  }
+      return { error: `unknown action: ${action}` }
     }
 
     await tabletJson('POST', '/api/voice/tools/smart-home', payload)