zabbix api manual at https://www.zabbix.com/documentation/2.2/manual/api/reference_commentary#common_get_method_parameters says that :

"output" is a "query".
above, one of the possible values for "query" is defined as "count - returns the number of retrieved records, supported by certain subselects."

that is not true - this flag alone makes it return all object ids. parameter countOutput has to be specified on top of that.

a) that is not clear in the documentation - 'output' docs mislead
b) i can't see a reason for countOutput - the same result can be achieved by specifying the desired id in 'output' directly