403 Forbidden: Insufficient privileges to complete the operation

Goal

Determine how to pinpoint the missing scope that caused a 403 error and understand the SDK’s behavior when a token expires in an application flow.

Constraints

The error payload for a 403 response only states “Insufficient privileges to complete the operation” and does not list the specific scope required. The Microsoft Graph .NET SDK does not automatically request a new token for application‑only flows when the bearer token has expired, leaving developers unsure whether the SDK will retry or if a manual refresh is needed.

Unresolved Questions

• Is there a documented method to retrieve the missing scope from a 403 response, or must developers infer it from the requested API endpoint?
• When using an application flow, does the SDK automatically refresh an expired token, or must the client explicitly acquire a new token?
• If the SDK does not refresh automatically, what is the recommended pattern for handling 401 InvalidAuthenticationToken errors in a production environment?