Hello @xandrico
I believe that you are looking for API rather than JSON, since you will get the response in JSON format.
The API for creating the request type: https://developer.atlassian.com/cloud/jira/service-desk/rest/api-group-servicedesk/#api-rest-servicedeskapi-servicedesk-servicedeskid-requesttype-post
You must be a registered user to add a comment. If you've already registered, sign in. Otherwise, register and sign in.