add the info from
COPYARTIFACT_BUILD_NUMBER_[JOB]="BUILD_NUMBER"

or the info that is contained in the console such as
Copied 1 artifact from "Tests" build number 6

to the Rest API xml
http://jenkinsserver:8080/job/[jobname]/[buildnumber]/api/xml

the info could look like

<copyartefact>
<jobname1>
<buildnumber>6<buildnumber>
<artefact>somefileA</artefact>
</jobname1>
<jobname2>
<buildnumber>12<buildnumber>
<artefact>somefileB</artefact>
</jobname2>
</copyartefact>