You are looking at the HTML representation of the XML format.
HTML is good for debugging, but is unsuitable for application use.
Specify the format parameter to change the output format.
To see the non HTML representation of the XML format, set format=xml.
See the complete documentation, or API help for more information. 
<?xml version="1.0"?>
<api>
  <query-continue>
    <alltransclusions gatcontinue="Boron_Release|4647" />
  </query-continue>
  <query>
    <pages>
      <page pageid="839" ns="0" title="OpenDaylight Controller:MD-SAL:Model Reference" />
      <page pageid="3320" ns="0" title="Documentation/Release Plans/Beryllium Release Plan" />
      <page pageid="3609" ns="0" title="ALTO:Architecture" />
      <page pageid="3989" ns="0" title="ALTO:Beryllium Installation Guide" />
      <page pageid="3990" ns="0" title="ALTO:Beryllium User Guide" />
      <page pageid="3991" ns="0" title="ALTO:Beryllium Developer Guide" />
      <page pageid="4238" ns="0" title="Documentation/Release Plans/Boron Release Plan" />
      <page pageid="4643" ns="0" title="ALTO:Boron User Guide" />
      <page pageid="4646" ns="0" title="ALTO:Boron Developer Guide" />
    </pages>
  </query>
</api>