https://learn.microsoft.com/en-us/azure/virtual-machines/extensions/key-vault-windows
The above documentation gives an important note:
Important
The 'authenticationSettings' property is required only for VMs with user assigned identities. It specifies identity to use for authentication to Key Vault.
Important
If you specify the 'msiClientId', then the 'msiEndpoint' property is required. Usually the value should be set to http://169.254.169.254/metadata/identity/oauth2/token.
I have an user assigned managed identity assigned to VMSS. And KeyVault access policy to allow this user assigned managed identity.
I have an AKV extension for VMSS. Is authenticationSettings really needed? The documentation seems to suggest that it is needed, but also seems to suggest it is needed only when msiClientId is specified.