This API should be publicly accessible without requiring a valid token to access, it artificially limits the domain of the API to impersonation tokens. The documentation page itself masks this requirement as you only enter the token to validate, not realising to access the site itself requires a valid token which is transparently passed along with the API request itself.
I strongly suggest you contact the RKD support team directly via https://my.refinitiv.com/ (chose Product "Refinitiv Knowledge Direct API") for this kind of product feature request.
Dears, We are integrating the Retrieve_item_3 service to get the MSCI index. In this, we need to get the Total Stocks in the index. But in the response, we don't find any field which is matching the 'Total Stocks' in the index .