addFeature for a polygon gives two different error messages

[MannusEtten]

i try to post the following message:

features=[{"geometry":{"rings":[[[203853.556499999,503811.715500001],[203878.6611,503761.506299999],[203891.213399999,503761.506299999],[203928.870299999,503736.401700001],[203941.422600001,503711.2971],[203966.527199998,503686.192499999],[203966.527199998,503748.954],[204004.184099998,503058.577399999],[203803.3473,502343.0962],[202598.326400001,502569.037700001],[202121.3389,503209.204999998],[202071.129700001,503635.9833],[202786.6109,503912.133900002],[203414.225900002,503924.6862],[203677.824299999,503899.581599999],[203828.451900002,503824.2678],[203853.556499999,503811.715500001]]],"spatialReference":{"wkid":28992}}}]&f=json

to the url:
http://localhost/ArcGIS/rest/services/dbk/FeatureServer/2/addFeatures

my client returns the message:
{"addResults":[{"objectId":-1,"globalId" : null,"success":false,"error":{"code":-2147221398,"description":"Geometry does not have Z Value(s)."}}]}

but if I use the example page of the rest api and fill in my post i get the following message:
{
  "error" :
  {
    "code" : 400,
    "message" : "Unable to complete  operation.",
    "details" : [
      "Invalid graphic features",
      "Invalid parameters"
    ]
  }
}

So what is wrong with my message to post?

[RaviNarayanan]

Mannus,

Please see the following help topic for more information regarding "Editing features with z-values in feature services":

http://help.arcgis.com/en/arcgisserver/10.0/help/arcgis_server_dotnet_help/index.html#//00930000164n...