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="Banks|35" />
  </query-continue>
  <query>
    <pages>
      <page pageid="1" ns="0" title="Hlavní strana" />
      <page pageid="16" ns="0" title="Okres Děčín" />
      <page pageid="18" ns="0" title="Pošta Děčín I Oblouková" />
      <page pageid="26" ns="0" title="Pošta Děčín VI Želenická" />
      <page pageid="27" ns="0" title="Pošta Děčín IX Teplická" />
      <page pageid="28" ns="0" title="Pošta Děčín XII Vilsnice" />
      <page pageid="29" ns="0" title="Pošta Jetřichovice" />
      <page pageid="32" ns="0" title="Město Benešov nad Ploučnicí" />
      <page pageid="33" ns="0" title="Město Česká Kamenice" />
      <page pageid="34" ns="0" title="Město Děčín" />
    </pages>
  </query>
</api>