Listar campos com select no metadados

achei este select:


select rdb$relation_fields.rdb$relation_name,
rdb$relation_fields.rdb$field_name,
case
when rdb$types.rdb$type_name = ´VARYING´ then ´VARCHAR´
else rdb$types.rdb$type_name
end field_type,
rdb$fields.rdb$field_length
from rdb$relation_fields
join rdb$fields
on rdb$fields.rdb$field_name =
rdb$relation_fields.rdb$field_source
join rdb$types
on rdb$fields.rdb$field_type = rdb$types.rdb$type and
rdb$types.rdb$field_name = ´RDB$FIELD_TYPE´
where (substring(rdb$relation_fields.rdb$relation_name from 1 for 4) <>
´RDB$´)
order by rdb$relation_fields.rdb$relation_name


eu procuro exatamente isso, só que com a descrição do campo também,
alguém sabe como fazer?