What about this:

```javascript
return $resource('/katello/api/providers/:id/:action',
            {id: '@id', 'organization_id': CurrentOrganization, 'provider_type': 'Custom'},
            {
                query:  {method: 'GET', params: {'provider_type': 'Custom'},
                save: {method: 'GET', params: {'provider_type': 'Custom'},
            }
        );
```

Does that not default the actions to provider_type Custom?