XSLT 3 : convert xml to json

The XML format that xml-to-json consumes is specified both in the XSLT 3.0 specification (www.w3.org/TR/xslt-30/#json-to-xml-mapping) as well as in the XPath and XQuery 3.1 function specification: www.w3.org/TR/xpath-functions/#json.

Basically all elements need to be in the namespace http://www.w3.org/2005/xpath-functions and are map, array, string, boolean, number etc., to reflect the JSON datatypes.

The error message suggests your input contains an element named wrapper in no namespace, so that is certainly not the right format for that function. You will need to use additional transformation steps to transform your XML to the one the function expects.