Using Zabbix with Active Agent, How to determine the correct key. (LLD)

I'm trying to do a discovery to get info from antivirus software.

In zabbix_agentd.conf i put this:

UserParameter=custom.discovery, cscript c:\soft\zabbix\av.vbs //NOLOGO

With this result:

{"data":[
{"{#DISPLAYNAME}": "ESET Endpoint Security 6.4.2014.2",
"{#PRODUCTSTATE}": "266240",
"{#TIMESTAMP}": "Tue, 18 Jul 2017 21:24:26 GMT"},
{"{#DISPLAYNAME}": "Windows Defender",
"{#PRODUCTSTATE}": "393472",
"{#TIMESTAMP}": "Thu, 10 Nov 2016 12:20:52 GMT"}
]}

My Discovery rule is this:

Name: Antivirus
Type: Zabbix Agent (Active)
key: custom.discovery

And i create this item prototype:

Name: Antivirus {#DISPLAYNAME}
Type: Zabbix Agent (Active)
Key: custom.discovery[ {#DISPLAYNAME}, PRODUCTSTATE]

My problem is when the item trying to get the "Productstate", the items are discovered correctly, but without value.

At the Configuration/Host/Item, i see the error "Item does not allow parameters" in each item created from the discovery.

Somebody can help me? Thx!