This API is used to Get Asset list
Please check example usage of Vision Helpdesk API

Operation : assets
Module : cmdb

$postfields["vis_module"] = "cmdb";
// This is the module under which you wish to perform operation

$postfields["vis_operation"] = "assets";
// This is the operation field

Below is example API URL to fetch assets

XML: 
http://visiononlinedemo.com/support/api/index.php? 
&vis_txtusername=admin
&vis_txtuserpass=21232f297a57a5a743894a0e4a801fc3 
&vis_modul<span id="selection-marker-1" class="redactor-selection-marker"></span>e=cmdb 
&am<span id="selection-marker-2" class="redactor-selection-marker"></span>p;vis_operation=assets 
&vis_page=0
&vis_encode=xml
JSON: 
http://visiononlinedemo.com/support/api/index.php? 
&vis_txtusername=admin 
&vis_txtuserpass=21232f297a57a5a743894a0e4a801fc3 
&vis_module=cmdb 
&vis_operation=assets 
&vis_page=0 
&vis_encode=json

OR use "access token" to fetch assets

XML: 
http://visiononlinedemo.com/support/api/index.php? 
&vis_txttoken=WXprMk1UY3dZV1V6WWpZeU16RmpOelF3TVdReE5UWTJOVGMyTm1VeU4yUT0= 
&vis_module=cmdb 
&vis_operation=assets 
&vis_page=0 
&vis_encode=xml
JSON 
http://visiononlinedemo.com/support/api/index.php? 
&vis_txttoken=WXprMk1UY3dZV1V6WWpZeU16RmpOelF3TVdReE5UWTJOVGMyTm1VeU4yUT0= 
&vis_module=cmdb 
&vis_operation=assets 
&vis_page=0 
&vis_encode=json