diff --git a/src/mcp_synology_filestation/tools/filestation.py b/src/mcp_synology_filestation/tools/filestation.py
index 2cbafb6..a829d80 100644
--- a/src/mcp_synology_filestation/tools/filestation.py
+++ b/src/mcp_synology_filestation/tools/filestation.py
@@ -151,7 +151,7 @@ def register_filestation(
                     "limit": limit,
                     "sort_by": sort_by,
                     "sort_direction": sort_direction,
-                    # DEBUG: no additional — testing if any additional causes 408
+                    "additional": json.dumps(["size"]),  # DEBUG: only "size"
                 },
             )
         except SynologyError as e: