Learning about SharePoint API's

[Adele_V]

Hi, 

I am learning about the SharePoint API's from the Documentation available and tried performing the actions through Postman tool.

I am able to do the Get request (for example: Get Folders) in the postman tool but when I am trying to perform Post request (for example: Delete Folder) then the error message is "Access denied. You do not have permission to perform this action or access this resource".

Can I know the reason for this??

[#2]

Performing from Postman you are essentially performing an external call and as such need to provide authentication, which can be done but is more complex to start.

Using a chrome Extension like SP Insider you can perform API calls (REST and Search) from within an authenticated session in the browser window and as such can skip the need to manually setup the authentication. This is generally how you webpart code will run also, within the context of the user's browser session.

[#3]

I am able to provide the authentication (generated the access token using client id, secret, Tenant id) but I couldn't perform post request API calls.
Is there anything to do with account permissions, just curios..
FYI: I am successful in retrieving the data (Get request API calls).