When you uncheck "Admin Password is required" option in Management console -> Environment-> Advanced_settings -> Webservices it gives an error.
Uncheck "Admin password is required" and save.
Error when trying to save by unchecking "Admin Password is required"
Identity Manager 14.x & v15
By default, Admin Password Required is set to true (checked).
The message "At least one type of authentication is required" is correct and expected. You really do need to have one of the authentication methods selected.
If you don't want to provide the admin password in your request you'll need to use either the WSS Token or SiteMinder Authentication.