The Channel Metadata API provides insights into the metadata associated with data channels in an Ably app. It overcomes the classic n-squared problem faced when all clients subscribe to receive updates about other clients joining and leaving an app. The API solves three key challenges: 1) Presence and the n-squared challenge, where it minimizes the number of messages sent by having only backend app server subscribe to presence updates; 2) Implementation effort, as developers can now subscribe to metadata changes without repeating work for every participant; and 3) Only publishing when someone is actually listening, allowing publishers to ensure they're only pushing data out when there are consumers. The API enables users to consume data via a pull mechanism using Ably's REST API or a push mechanism by subscribing to updates.