Using MarkLogic REST API, when I set Accept to multipart/mixed I see the response in the format:
--BOUNDARY
    Content-Type: application/xml
    Content-Disposition: attachment; filename="/hcp/458.xml"; category=content; format=xml
    Content-Length: 412
<?xml version="1.0" encoding="UTF-8"?>
<hcp xmlns="http://schemas.com">
  <id>458</id>
  <tenantId>2</tenantId>
  <firstName>Hoongoong</firstName>
  <middleName/>
  <lastName>Tangyy</lastName>      
</hcp>
--BOUNDARY
Content-Type: application/xml
Content-Disposition: attachment; filename="/hcp/2.xml"; category=content; format=xml
Content-Length: 409
<?xml version="1.0" encoding="UTF-8"?>
<hcp xmlns="http://schemas.com">
  <id>2</id>
  <tenantId>3</tenantId>
  <firstName>Hoong</firstName>
  <middleName>F</middleName>
  <lastName>Tang</lastName>     
</hcp>
--BOUNDARY
Is there a way via some tweak or applying transformation to display the result as a single document (containing documents as child element) instead of multiple documents separated by boundary?
<results>
   <hcp>
      <id>458</id>
       .....
    </hcp>
   <hcp>
      <id>2</id>
     ......
   </hcp>
</results>
				
                        
You can execute a search with the
REST API, setting the Accept header toapplication/xml.Specify an
extract-document-dataoption of all to get the entire documents.http://docs.marklogic.com/guide/rest-dev/appendixb#id_18313
You can use a document-query if you just need to list specific documents:
http://docs.marklogic.com/guide/search-dev/structured-query#id_27172
You can also transform the search response on the server:
http://docs.marklogic.com/guide/rest-dev/search#id_94556
Hoping that helps,