Data Warehouse Segment Breakdowns with Report API

The addition of breakdown segments for Data Warehouse was very useful.  Now I'm trying to move some of the reports I've created using the DW UI into scripts using the 1.3 reporting API, and I don't see any documentation of how to specify the breakdown segments.

The parameters for the DataWarehouse.Request() call are:

{ "Breakdown_List":[ "(string)" ], "Contact_Name":"(string)", "Contact_Phone":"(string)", "Date_From":"(string)", "Date_Granularity":"(string)", "Date_Preset":"(string)", "Date_To":"(string)", "Date_Type":"(string)", "Email_Subject":"(string)", "Email_To":"(string)", "FTP_Dir":"(string)", "FTP_Host":"(string)", "FTP_Password":"(string)", "FTP_Port":"(int)", "FTP_UserName":"(string)", "File_Name":"(string)", "File_Type":"(string)", "Metric_List":[ "(string)" ], "Report_Description":"(string)", "Report_Name":"(string)", "Segment_Id":"(int)", "rsid":"(string)" }

I'm able to apply a global segment, but not segment breakouts (I need more than one).  Is this functionality present but undocumented, or is it just not available through the API?