Zendesk Recipe: Send greetings with an agent's name when a chat is assigned to the agent

Create a trigger action with the following payload to call Delayer webhook:

{    
   "delay": 0,
   "message": {
       "author": {
           "type": "business",
           "displayName":"{{ticket.assignee.name}}"
       },
       "content": {
           "text": "Hello!",
           "type": "text"
       }
   },
   "ticket_id": "{{ticket.id}}"
}

where 
delay is the delay in seconds. 
message structure is in Sunshine conversation format.
displayName is the name of the sender.
text is the message text. 
{{ticket.assignee.name}} is a placeholder for the assignee name.

You can see the list of Zendesk placeholders here:
https://support.zendesk.com/hc/en-us/articles/4408886858138-Placeholder-reference-for-business-rules