Introspect it

my $description = Class->meta->metadescription; # Ernst::Description::Container::Moose
$description->get_attribute_list;               # ('attribute')
$description->get_attribute('attribute');       # Ernst::Description::String
$description->get_attribute('attribute')->max_length; # 42

my $attribute = Class->meta->get_attribute('attribute');
$attribute->metadescription->max_length; # 42