Please consider to allow adding [] or [""] to a parameterless item key.

This would allow all item keys to be possibly used in the SINGLETON LLD approach.

Currently items that don't accept parameters like for example 

agent.ping

 can't be used as 

agent.ping[{#SINGLETON}]

 in LLD. The resulting item would then be 

agent.ping[]

 and becomes unsupported with error:

ZBX_NOTSUPPORTED: Too many parameters.

while there are actually no parameters defined.

Therefore I would propose for the Zabbix Agent to accept 

item.key[], item.key[""] and/or item.key['']

as equals to 

item.key 

and only return the "Too many parameters" error when there are actually parameters given like in

item.key["param1"]