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>
    <allfileusages gafcontinue="Manuscrito_230_BNC_-_fol_16r.jpg|70" />
  </query-continue>
  <query>
    <pages>
      <page pageid="60" ns="0" title="Manuscrito 230 BNC/fol 11r" />
      <page pageid="61" ns="0" title="Manuscrito 230 BNC/fol 11v" />
      <page pageid="62" ns="0" title="Manuscrito 230 BNC/fol 12r" />
      <page pageid="63" ns="0" title="Manuscrito 230 BNC/fol 12v" />
      <page pageid="64" ns="0" title="Manuscrito 230 BNC/fol 13r" />
      <page pageid="65" ns="0" title="Manuscrito 230 BNC/fol 13v" />
      <page pageid="66" ns="0" title="Manuscrito 230 BNC/fol 14r" />
      <page pageid="67" ns="0" title="Manuscrito 230 BNC/fol 14v" />
      <page pageid="68" ns="0" title="Manuscrito 230 BNC/fol 15r" />
      <page pageid="69" ns="0" title="Manuscrito 230 BNC/fol 15v" />
    </pages>
  </query>
</api>