All responses are, by default, returned in a REST-friendly XML format unless a format
parameter is sent and its value is not rest
.
<rsp stat="ok">
<api_key>9bb013121e8f3650f350b622a1735442</api_key>
<foo>bar</foo>
<method>rtm.test.echo</method>
</rsp>
<rsp stat="fail">
<err code="112" msg="Method "rtm.test.ech" not found"/>
</rsp>