Can't create a ticket via API

Can't create a ticket via API

HI, I am trying to create a ticket, as per the documentation

https://desk.zoho.com/DeskAPIDocument#Tickets%23Tickets_Createaticket

I am passing in the orgId and authtoken in the header and the two other required fields as perams 

https://desk.zoho.com/api/v1/tickets?subject="This is a test"&departmentId=254992000002404124
and when executed I am getting a 400 Bad Request, what is missing?