/services/recommendation_service.proto

--- v19/services/recommendation_service.proto   2025-08-05 14:37:33.000000000 +0000
+++ v20/services/recommendation_service.proto   2025-08-05 14:37:47.000000000 +0000
@@ -742,6 +742,16 @@
   // following recommendation_types: CAMPAIGN_BUDGET
   optional bool target_content_network = 19
       [(google.api.field_behavior) = OPTIONAL];
+
+  // Optional. Merchant Center account ID.
+  // This field should only be set when advertising_channel_type is
+  // PERFORMANCE_MAX. Setting this field causes RecommendationService
+  // to generate recommendations for Performance Max for retail
+  // instead of standard Performance Max.
+  // This field is optional for the following recommendation_types:
+  // CAMPAIGN_BUDGET
+  optional int64 merchant_center_account_id = 20
+      [(google.api.field_behavior) = OPTIONAL];
 }

 // Response message for