I'm using HTTP agent to get the our Rundeck health state throught its dedicated endpoint. As a code, this is

}}{{➜  ~ curl -sL 'https://rundeck.company.com/api/27/metrics/healthcheck?authtoken=MYUSERTPOKEN'{{                                              }}
{"dataSource.connection.time":{"healthy":true,"message":"Datasource connection healthy with timeout 5 seconds"},"quartz.scheduler.threadPool":{"healthy":true%  }}

As you can see, there are two keys with dots, dataSource.connection.time to begin with. As per JSON path spec, I should be able to get the sub key healthy with

   $.['{{dataSource.connection.time'].healthy}}

And some peoples in QAs reported being successful (outside of zabbix context) with

   $.\"dataSource.connection.time\".healthy

Zabbix refuses that, made some tests despecializing characters :  [ and ' and " and \ seems to be illegal for the jsonpath field.

Workaround, use an ugly regexpr.