diff --git a/proto/cosmos/tx/signing/v1beta1/signing.proto b/proto/cosmos/tx/signing/v1beta1/signing.proto
index a87b405f93..6901b6548c 100644
--- a/proto/cosmos/tx/signing/v1beta1/signing.proto
+++ b/proto/cosmos/tx/signing/v1beta1/signing.proto
@@ -7,6 +7,13 @@ import "google/protobuf/any.proto";
 option go_package = "github.com/cosmos/cosmos-sdk/types/tx/signing";
 
 // SignMode represents a signing mode with its own security guarantees.
+//
+// This enum should be considered a registry of all known sign modes
+// in the Cosmos ecosystem. Apps are not expected to support all known
+// sign modes. Apps that would like to support custom  sign modes are
+// encouraged to open a small PR against this file to add a new case
+// to this SignMode enum describing their sign mode so that different
+// apps have a consistent version of this enum.
 enum SignMode {
   // SIGN_MODE_UNSPECIFIED specifies an unknown signing mode and will be
   // rejected.