Hi,

 
I noticed something missing in the Rocket Chat integration documentation https://www.zabbix.com/integrations/rocketchat
The media type requires that a variable {ZABBIX.URL} be defined for it to work but this is mentioned nowhere and the error you get when you don't set it is not very helpful (error 400 "Invalid href value provided")
 
Ideally you could add something like this (pulled from the Pushover integration doc) :
 

Set {$ZABBIX.URL} global macro

Go to Administration->General (Macro) and create new macro that points to your Zabbix frontend

{$ZABBIX.URL} = https://myzabbix.local

Since it took me quite a while to find this, it would definitely be helpful to add it to the doc.

Regards.