Create Message
Send an in-app message into a conversation.
sender_id must be an accepted member of your org and an active participant
of the target conversation (404 otherwise) — the API can’t impersonate a family
member or post into a thread it isn’t part of. The message is sent as plain text,
visible to everyone in the thread, and the normal bell/email notifications fire.
Honours Idempotency-Key.
Authorizations
Org API key as Token token=ei_live_...
Headers
Body
POST /v1/messages → send an in-app message into a conversation. sender_id
must be an accepted org member who is an active participant of the conversation.
The message is always inserted as message_type='text', visibility='everyone'
(so the existing notify/email/mirror triggers fire normally); system/private
message types are not settable via the API.
Response
Successful Response
One message in a thread. Only visibility='everyone' (non-deleted) messages
are exposed by the read endpoints — family-private (student_only/parent_only)
messages are never returned.