The action type ("subscribe_depth" or "subscribe_depth_update").
OptionalchangesIncremental changes (present on updates).
Market identifier.
Optionalonchain_On-chain timestamp.
Optionalseen_Server-observed timestamp.
OptionalviewFull order book view (present on snapshots).
A WebSocket depth update message.
Can be either a full snapshot (
action: "subscribe_depth") or an incremental update (action: "subscribe_depth_update").