I wrote a Stored Procedure which sets the description. I need to run the Stored Procedure after deployment which is kind of a workaround but I'm fine with this solution.
Here is the code:
-- Folder Description: QC - Internal Reports
UPDATE DBReporting.dbo.Catalog
SET Description = 'restricted to department QC'
WHERE Type = 1 -- Folder
AND Name = 'QC - Internal Reports';
Bonus:
You can also hide (Sub)Reports using the Catalog Table in the Reporting Database. I use the Report description in Visual Studio to identify the reports which i want to hide.
-- Hides Reports
UPDATE DBReporting.dbo.Catalog
SET Hidden = 1
WHERE Type = 2 -- Report
AND Description = 'Hidden';
-- Hide Datasource Folder
UPDATE DBReporting.dbo.Catalog
SET Hidden = 1
WHERE Type = 1 --Folder
AND Name = 'Data Sources';