All documentation about API is available here: https://confluence.e-loreal.com/display/APICOE/HIP+API+Section 

To access the UNIKA "PRODUCT HIERARCHY" API, your application must be first authorized on APIGEE: please send your authorization request to the API owner, by providing your application ID.

One authorized, your application must present a valid token for every API call. Here is the scope to specify to request for an access token for the UNIKA "PRODUCT HIERARCHY" API:

• DEV: api://2703cf84-3987-472e-9604-37f847fea6ac/.default
• QUAL: api://241d98ee-80bb-493e-8f9a-16b12737f479/.default
• SIMU: api://de9562dd-fb85-474c-8ab7-41539e9dff26/.default
• PROD: api://92ebccb6-4781-4e53-b463-063296554554/.default

Note that for UNIKA "PRODUCT HIERARCHY" API, your application do not need any specific API permission to be granted in Azure AD.