By default, when a custom metadata annotation is added to or replaced in a namespace, HCP checks whether it contains well-formed XML. If the XML is not well-formed, HCP rejects the annotation.
For any given namespace, you can choose to allow users to provide annotations in non-XML formats (for example, as thumbnail images to accompany large objects with image content). In this case, you need to disable custom metadata XML checking for the namespace so that HCP accepts non-XML annotations.
XML checking applies only when annotations are added to or replaced in a namespace. It does not apply to annotations that already exist in the namespace.
You can enable or disable custom metadata XML checking for a namespace at any time.