Using a JSON request in AdCenter

Question

I can't find any example in the docs, and searching the forums resulting in nothing, so I'm posting.

http://msdn.microsoft.com/en-us/library/ff728488.aspx says GetCampaignsByIds can use XML or JSON, but it doesn't give any examples of how to post a request using JSON.  Also, the feed at https://adcenterapi.microsoft.com/Api/Advertiser/v7/CampaignManagement/CampaignManagementServiceREST.svc/help explicitly says:

Request Format:  XML or JSON

Based on the XML example:

<GetCampaignsByIdsRequest 

xmlns="http://schemas.datacontract.org/2004/07/HostedService.CampaignManagementService.Rest" 

xmlns:i="http://www.w3.org/2001/XMLSchema-instance">

  <CampaignIds 

xmlns:d4p1="http://schemas.microsoft.com/2003/10/Serialization/Arrays">

    <d4p1:long></d4p1:long>

  </CampaignIds>

</GetCampaignsByIdsRequest>

I've tried posting a JSON request of:

{"GetCampaignsByIdsRequest": {"CampaignIds": [NNNNNNNN, NNNNNNNN]}}

And I've also tried just:

{"CampaignIds": [NNNNNNNN, NNNNNNNN]}

But I'm getting this back from the server:

{u'Errors': [{u'ErrorCode': u'InternalError', u'Message': u'An internal error has occurred.', u'Code': 0, u'Detail': None}], u'TrackingId': u'63637dfa-4ee2-4e4c-a229-d01eb3d41652'}

I'm using a request URL of:

https://adcenterapi.microsoft.com/Api/Advertiser/v7/CampaignManagement/CampaignManagementServiceREST.svc/customer/account/NNNNNN/campaign?$field=ids&format=json

Has anyone successfully used the REST API to post a JSON request? Is there an example in the docs as to how to structure the JSON data when sending a request?

Thanks!

j