...

cxx/mcc_mount_telemetry.h

@@ -19,8 +19,12 @@ namespace traits
 
 template <typename T>
 concept mcc_mount_telemetry_c = requires(T t, const T t_const) {
+    typename T::error_t;
     typename T::mount_telemetry_data_t;
-    { t.update() };
+
+    { t_const.errorString(std::declval<typename T::error_t>()) } -> mcc_formattable;
+
+    { t.update() } -> std::same_as<typename T::error_t>;
 
     { t_const.data() } -> std::same_as<typename T::mount_telemetry_data_t>;
 };