How to set DESCRIPTION field in system catalog using code

See more:

SQL-Server

SQL-Server-2008

T-SQL

Sounds easy enough ...

EXECUTE sys.sp_catalogs 'server\instance'

returns:

CATALOG_NAME                DESCRIPTION
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
x                   NULL
y               NULL
z               NULL
master              NULL
model               NULL
msdb                NULL
Northwind           NULL
ReportServer$instance       NULL
ReportServer$instanceTempDB NULL
tempdb              NULL
r               NULL

This is actually a more general question that boils down to "How to set (most) ANY 'NULL' system table value to, presumeably a "user" defined value, programmatically".