Changes to List generic engines

the response property results/items/description became required for the status 200

the response property results/items/documentation_url became required for the status 200

the response property results/items/id became required for the status 200

the response property results/items/name became required for the status 200

the response property results/items/schema became required for the status 200

the response property results/items/url became required for the status 200