I came across a very informative document on GitHub about the structure of metadata that relays provide to clients over HTTP. This document provides valuable insights into the different fields that are required for relay metadata, as well as those that can be omitted. It also explains how clients should handle unknown fields.

One interesting aspect of this document is its emphasis on supporting CORS requests with appropriate headers. This is important because it ensures that clients can access the metadata they need without any issues. Additionally, the document includes information on alternative contacts and supported NIPs, which can be useful for anyone looking to set up their own relay.

Overall, I found this document to be a great resource for anyone interested in learning more about relays and their metadata structure.