It looks like the OData $count parameter is not (yet?) supported in the Microsoft Graph API v1.0 for OneDrive.
Request URL: https://graph.microsoft.com/v1.0/me/drive/root/children?$count=true
Response:
{
"error": {
"code": "",
"message": "The query specified in the URI is not valid. Query option 'Count' is not allowed. To allow it, set the 'AllowedQueryOptions' property on EnableQueryAttribute or QueryValidationSettings.",
"innerError": {
"request-id": "e65aff74-1c6f-434b-8cd3-04e0c247fb71",
"date": "2016-10-19T09:48:39"
}
}
}
Is this understanding correct?