Returns album-level metadata with a structured, documented response containing photo counts, collection status, and unread message counts per album.

The response is cached server-side for 1 minute; the same TTL is advertised via the Cache-Control header and the cache_ttl_seconds field in the body.

If album_ids is omitted, all non-deleted albums for the account are returned, capped at 500. Pass album_ids explicitly for stable, bounded responses.

Related: Get information about an album, Get content count, List albums.

Supports If-None-Match / ETag caching. The ETag rotates with the 60-second server cache bucket.