On Transact SQL language the sp_addextendedproperty is part of Database Engine Stored Procedures and adds a new extended property to a database object.

Sp_addextendedproperty syntax:

sp_addextendedproperty
[ @name = 'property_name' ]
[ , [ @value = 'value' ]
   [ , [ @level0type = 'level0_object_type' ]
     , [ @level0name = 'level0_object_name' ]
         [ , [ @level1type = 'level1_object_type' ]
           , [ @level1name = 'level1_object_name' ]
               [ , [ @level2type = 'level2_object_type' ]
                 , [ @level2name = 'level2_object_name' ]
] ] ] ] ;

Add an extended property to a table:

USE model;
GO
EXEC sys.sp_addextendedproperty
@name = N'Test example',
@value = N'This is an example.',
@level0type = N'SCHEMA', @level0name = 'dbo',
@level1type = N'TABLE', @level1name = 'my_table';
GO