To get you desired output your configuration should like:
config.model Article do
list do
field :title
field :created_at
field :updated_at
end
edit do
field :title
field :description, :string do #use second parameter to set field type
required true #this will just set a hints text
#to set max length use:
html_attributes do
{:maxlength => 600} #dont use 600 as maxlength for a string field. It will break the UI
end
end
end
end