How to set a GUID field type

[JamesMolohon]

I have a feature service that I want to add items to using the editor.  I have an attribute that I want to assign a guid to:

UNIQUEID (Type: esriFieldTypeGUID, Alias: UNIQUEID, Length: 38 )

How do I assign a guid to this?  In fiddler I receive this error for addResults:
code=-2147219887
description=Setting of Value for UNIQUEID failed.

I haven't found how to format my GUID yet for this to work.  Please help.

Thanks!
James

[JamesMolohon]

I have solved this by testing with the rest endpoint update features tool.  Apparently I need to wrap the guid in curly braces.

[{"attributes" : {
        "OBJECTID" : 5,
        "UNIQUEID" : "{c611d5cb-9df3-46b5-9312-84ba99251955}",
      }
}]