diff --git a/modal_proto/api.proto b/modal_proto/api.proto
index f8edc5dfb..8afb1b594 100644
--- a/modal_proto/api.proto
+++ b/modal_proto/api.proto
@@ -1512,6 +1512,7 @@ message FunctionGetOutputsItem {
   double input_started_at = 7;
   double output_created_at = 8;
   uint32 retry_count = 9;
+  string fc_trace_tag = 10; // datadog function call trace tag
 }
 
 message FunctionGetOutputsRequest {