Sometimes you need to get list of available operations in the Sharepoint REST API endpoint. Let’s say we want to check operations available for /_api/SitePages endpoint.
First of all we need to get authentication cookies. In order to get them lunch Fiddler and open e.g. Sharepoint landing page (/_layouts/15/Sharepoint.aspx) which is opened from App launcher > Sharepoint. On this page there will be several REST API calls which will contain Cookies header. E.g. /_api/GroupSiteManager/CanUserCreateGroup:
From this Fiddler view copy value of Cookie header.
After that launch Postman and create request on endpoint in question: /_api/SitePages. In Headers section add Cookie, put value copied from Fiddler and click Send:
In the response it will return list of relative endpoint operations available under selected endpoint. In this example they are:
Note that this method doesn’t return POST/PUT endpoints unfortunately.