diff --git a/protoc-gen-openapiv2/options/openapiv2.proto b/protoc-gen-openapiv2/options/openapiv2.proto
index 234d8408237..460a545336a 100644
--- a/protoc-gen-openapiv2/options/openapiv2.proto
+++ b/protoc-gen-openapiv2/options/openapiv2.proto
@@ -176,6 +176,8 @@ message Operation {
   // See: https://swagger.io/docs/specification/2-0/swagger-extensions/
   map<string, google.protobuf.Value> extensions = 13;
   // Custom parameters such as HTTP request headers.
+  // See: https://swagger.io/docs/specification/2-0/describing-parameters/
+  // and https://swagger.io/specification/v2/#parameter-object.
   Parameters parameters = 14;
 }