Edit:
After reading document again: https://developers.facebook.com/docs/facebook-login/access-tokens.
I realize facebook has 4 types of token:
- User Access Token
- App Access Token = app_id|app_secret
- Page Access Token
- Client Token
App Access Token is used to read the app settings (not the user info).
And "https://graph.facebook.com/me" is for user info so we need to use User Access Token
example of using app access token:
https://graph.facebook.com/APP_ID/roles?&access_token=APP_ID|APP_SECRET