The Kekanto API requires an API Key which comes with a Secret Key. Requests are usualy made using the HTTP GET Method.
The response format is JSON by default, but you can change the output to XML by adding the .xml extension at the end of the resource.
URI. e.g. the resource places (http://api.kekanto.com/v1/places) can have it's output formatted to XML by using the URI http://api.kekanto.com/v1/places.xml instead.
Check the Requesting an API key page to understand how it happens.