If the API is executed successfully, here is the description of response attributes, which returns to the form of JSON.
Staff added to event -> In permissions select Staff.
Here are the possible error messages, which return if any condition gets failed or required data is missing for processing.
User has already logged in at website. Can't change email now!
You have already added this team member.
This email address is already assigned. You can not change existing staff with this email address.
Cannot make last event admin as staff.
Cannot make last event Exhibitor Admin as Lead Retriever.