using xdmp:eval in REST Service in Marklogic - rest

Question

I am using the below REST service to insert the document(from DB Ingestion) into Rest DB which is configured for this service. I am using POST method and sending parameters in form-data.
URL: http://{hostname}:8010/v1/addDocument.
The issue is that the xml($DirectoryListing) picked from Ingestion DB is getting automatically serialized into text, so I am not getting the xml for insertion.
This is working fine when this code is directly ran on Qconsole, but from rest service call its not working.
ML Version I am using is 7.0-2.3​
Please help me on this.
let $PrefixURI := "/docs/"
let $Path := fn:concat('/processing/',$transId,'/validDocs/')
let $_ := xdmp:log(fn:concat("Path",$Path))
let $DirectoryListing as node() :=
xdmp:invoke-function(
function() {
xdmp:directory($Path)
} ,
<options xmlns="xdmp:eval">
<database>{xdmp:database("Ingestion")}</database>
</options>
)
let $logs :=
element docsUris {
for $FileEntry in $DirectoryListing
let $Filename := functx:substring-after-last(xdmp:node-uri($FileEntry),'/')
let $docUri := fn:concat($PrefixURI, $Filename)
let $_ := xdmp:log(fn:concat("uri",$docUri))
let $contents := $FileEntry
let $_ := xdmp:log(fn:concat("adding document",$contents))
return
(: Insert the document :)
(dls:document-insert-and-manage(
$docUri,
fn:false(),
$contents,
"created",
(xdmp:permission("dls-user", "read"),
xdmp:permission("dls-user", "update")),
"historic"),
xdmp:document-add-collections(
$docUri,
"latest"),
xdmp:document-remove-collections(
$docUri, "historic")
)