When planning to use REST API to handle object data, this KB will explain how to check for all available object fields through REST API
Service Desk Manager 17.4
REST Web Services Enabled
In order to see all the available fields through REST API, you can check the wadl output by accessing the following link:
http://<server>:8050/caisd-rest/rest_access/?_wadl
Note: 8050 is the default port for REST API.
Update accordingly if you are using a different port in your environment
This will generate an .xml page.
This page will contain all the available fields under each objects individual section
Example: /In for incidents.