The following syntax:
### List Webhooks [GET /webhooks]
+ Request
+ Headers
Authorization: Bearer <API_KEY>
+ Response 200 (application/json)
+ Attributes (array[Webhook])
doesn't look like an array when it's rendered in Apiary. See below.
Did something change?

Have you tried the new Apiary Documentation renderer? Many issues with rendering Data Structures have been fixed on it. I just tried your example and it renders as expected. https://help.apiary.io/tools/interactive-documentation-v4/