In my earlier post I pointed out that this data is NOT in a "hidden table" that is not accessible to the user. This information is in fact in sysproperties table and the column that contains the description is called [Value] with a datatype of sql_variant.
If you ask me (and I know you didn't), the desingn of this functionality is pathetic. Whoever came up with this hairbrained scheme obviously didn't know, or care, anything about good database design. You would almost be better off using an Excel spreadsheet to maintain your metadata.
I long ago gave up using the SQL server extended properties for documentation purposes. Neither ErWin or ER Studio reads or writes to the sysproperties table and since I have used both (currently ER Studio) why would I create extra work for myself?
If you don't use a capable modeling tool and want to keep your meta data in the database, I'd highly recommend that you "roll your own" to suit your needs. I have done this on occasion and it has proven to be a more workable solution than dealing with the extended properties nonsense.
If most people are not willing to see the difficulty, this is mainly because, consciously or unconsciously, they assume that it will be they who will settle these questions for the others, and because they are convinced of their own capacity to do this. -Friedrich August von Hayek