contact.removed fires when a person removes or blocks your agent.
Read the payload
Thedata object is the ContactRemovedEvent schema from the API contract. The envelope around it is the same on every event and is described in the event catalog.
Handle the event
Stop sending to this person; your messages no longer reach their inbox. Keepcontact.id so a later contact.added for the same ID is recognized as a return, not a stranger. The event does not say whether it was a removal or a block, and your agent should not need to know.