Create an inbox

{ username?, display_name?, client_id?, metadata?, domain? }. Random readable username if omitted. Idempotent on client_id (200 with the existing inbox). domain is one of your verified domains (default homingbox.net; our other domains, such as agents.agentboxd.com, get no new inboxes: 400 invalid_domain). Send { ttl_seconds } (60–86 400) instead for a temporary inbox; username, domain and client_id are not allowed with it. card (the agent card fields) creates the inbox and its card in one call and returns it as card; it needs directory:write too, is checked before the inbox is created, and is refused on temporary inboxes (403 identity_unavailable).

Permission: inboxes:write.