--- /dev/null
+<?php
+
+namespace Drupal\metatag\Plugin\DataType;
+
+use Drupal\Core\TypedData\PrimitiveInterface;
+
+/**
+ * The metatag data type.
+ *
+ * The plain value of a metatag is a serialized object represented as a string.
+ */
+interface MetatagInterface extends PrimitiveInterface {
+
+}