Outgoing Webhooks customization

I am trying to use outgoing webhooks to send information to an external tool. It is partially working fine but when I try to use the "requester.name" and "technician.name" variables it doesn't return any value. However "requester.email_id" fetches the mail address. Below is the json payload that I am using:

{
"message": "${subject}",
"description": "${description}",
"requester_name": "${requester.name}", //this doesn't fetch any value
"requester_email": "${requester.email_id}",
"technicain_name": "${technician.name}", //this doesn't fetch any value
"email": "${technician.email_id}",
"priority": "${priority.name}",
"status": "${status.name}",
"ticket_number": "${id}",
"ticket_url": "https://sdpondemand.manageengine.in/app/itdesk/ui/requests/${id}/details",
"ticket_created_time": "${created_time}",
"ticket_due_by_time": "${due_by_time}",
"source": "ServiceDesk Plus OnDemand"
}