LLD rule using external check-type becomes unsupported with JSON as error message

[chojin]

I have created a script that queries a remote device but should be run by the zabbix server itself and returns valid LLD JSON. (checked with jsonlint)
Using zabbix 3.4.2 I have then created a Discovery rule of the type "External Check" which calls this script.
I expected that the output of the script would be interpreted by the discovery rule, however, the rule becomes "unsupported" and the error message is the output of the script: the JSON code, capped however to 2048 characters.
Is 2048 characters a limitation of the external check method? or why doesn't this work ?

[chojin]

nevermind.. I added an explicit "exit 0" to the script and now it works. I found the remark in the documentation that an external check would become unsupported if the exit code was not 0.