can we use xdmp:document-insert in mlcp transformation query?

Question

I am trying to load binary files(PDF) via mlcp and using transformation method to load few metadata xml for each pdfs load via mlcp.

But getting below error -

xmlns:error="http://marklogic.com/xdmp/error" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">XDMP-ARGTYPE: (err:XPTY0004) map:get(<a>text</a>, "uri") -- arg1 is not of type map:map</error:format-string>

Please let me know how to achieve this.