Magento 2 how to pass if exist search criteria in rest api call

I need to filter getList records in my rest api call.
I have following:

searchCriteria[filter_groups][0][filters][0][field]=city_ref&searchCriteria[filter_groups][0][filters][0][condition_type]=notnull

But it returns all records to me, even if city_ref isn’t exist in the record.
I need url parameter like above, because i pass it in ajax.
How to do it?