diff --git a/include/adclib/adclib_netmsg.h b/include/adclib/adclib_netmsg.h
index 1583ef0..5f65537 100644
--- a/include/adclib/adclib_netmsg.h
+++ b/include/adclib/adclib_netmsg.h
@@ -50,6 +50,11 @@ public:
         return std::ranges::equal(this->_key, ADCLIB_NETMSG_KEYWORD_ACK);
     }
 
+    bool isERR() const
+    {
+        return std::ranges::equal(this->_key, ADCLIB_NETMSG_KEYWORD_ERR);
+    }
+
     bool isCMD() const
     {
         return std::ranges::equal(this->_key, ADCLIB_NETMSG_KEYWORD_CMD);
@@ -74,20 +79,34 @@ public:
 
     error_t createERR(error_t err)
     {
-        return this->setKey(ADCLIB_NETMSG_KEYWORD_ERR, err.value());
+        return this->setKeyValue(ADCLIB_NETMSG_KEYWORD_ERR, err.value());
     }
 
-    template <snplib::snplib_serializable_c ATTR_NAME_T, snplib::snplib_serializable_c ValueT>
-    error_t createSET(ATTR_NAME_T&& attr_name, ValueT&& value)
+    template <snplib::snplib_serializable_c ATTR_NAME_T, typename... ArgTs>
+        requires(sizeof...(ArgTs) > 0)
+    error_t createSET(ATTR_NAME_T&& attr_name, ArgTs&&... args)
     {
-        return this->setKeyValue(ADCLIB_NETMSG_KEYWORD_SET, std::forward<ATTR_NAME_T>(attr_name),
-                                 std::forward<ValueT>(value));
+        auto err = this->setKeyValue(ADCLIB_NETMSG_KEYWORD_SET, std::forward<ATTR_NAME_T>(attr_name));
+        if (err) {
+            return err;
+        }
+
+        return this->appendValue(std::forward<ArgTs>(args)...);
     }
 
-    template <snplib::snplib_serializable_c ATTR_NAME_T>
-    error_t createGET(ATTR_NAME_T&& attr_name)
+    template <snplib::snplib_serializable_c ATTR_NAME_T, typename... ArgTs>
+    error_t createGET(ATTR_NAME_T&& attr_name, ArgTs&&... args)
     {
-        return this->setKeyValue(ADCLIB_NETMSG_KEYWORD_GET, std::forward<ATTR_NAME_T>(attr_name));
+        auto err = this->setKeyValue(ADCLIB_NETMSG_KEYWORD_GET, std::forward<ATTR_NAME_T>(attr_name));
+        if (err) {
+            return err;
+        }
+
+        if constexpr (sizeof...(ArgTs)) {
+            return this->appendValue(std::forward<ArgTs>(args)...);
+        }
+
+        return {};
     }
 
     template <snplib::snplib_serializable_c CMD_NAME_T>