ticketsCountByFieldValues

ticketsCountByFieldValues

Hi Zoho Team,
Just to check how can I include customfields to the url string.
currently I'm using this.
url :"https://desk.zoho.com/api/v1/ticketsCountByFieldValues?accountId=xxxxxxxxxxx&departmentId=xxxxxxxxxxxxxx&field=statusType,status"

If I add customFields {Subcategory:Publishing} - execution failed: error due to internal exception