Exactly which API are you using? If it's to fetch a report, response is one of report export (pdf, html, xls, xlsx, rtf, csv, xml, docx, odt, ods, jrprint) so you'll be able to get it in xml format. Other API which doesn't return a report will return either a xml or json depending on your request header.
Thank you for your response.
I am using below url to get Report from server.
In the output its displaying whole html page as i have used ".html". But i need is there any option availble to get plain xml or json format as a response of above url.