REST APIs : Available operations and endpoints : Base structure
  
Base structure
All URIs in the REST API use the following base:
 
Observer Apex
https://hostname/oa/api/
Matrix
https://hostname/api/
Observer Management Server (OMS)
https://hostname/oms/api/
Observer
https://hostname/obs/api/v1/
Note: A secure HTTP session is required. Therefore, all requests must be sent to https://. Sending a request to http:// will fail.
For example, if you want to retrieve a list of users from Apex you would use an HTTP GET method. The GET request would be sent to https://hostname/oa/api/users/.