Start a Chat from Inbox is a POST on /premium/v2/{account_id}/inboxes/{inbox_id}/chats/send, part of the inboxes family of the MakeHybrid Premium API. Every request carries your own key in an X-API-KEY header; the key decides which organisation you are and therefore which LinkedIn accounts you may name.
The request
curl -X POST "https://makehybrid.com/premium/v2/$ACCOUNT_ID/inboxes/$INBOX_ID/chats/send" \
-H "X-API-KEY: $MAKEHYBRID_KEY" \
-H "content-type: application/json" \
-d '{}'
What goes in the path
- account_id — the connected LinkedIn account to act as. It must be one your own key connected; any other id answers 404.
- inbox_id — an id returned by an earlier call in this family.
What comes back when it does not work
- 401 — the key is missing, wrong or revoked.
- 402 — the plan is not paid for. Premium answers this once a trial has ended.
- 404 — either the thing is not there, or the account id is not yours. The two are deliberately the same answer, so ids cannot be probed.
- 429 — too many requests, or LinkedIn throttling the account. Waiting is the only fix; trying again sooner extends it.
- 503 — LinkedIn or the hop in front of it did not answer. The body carries the bare status it saw.
Every error is JSON in the same shape: {"type":"errors/<code>","status":<n>,"detail":"..."} — so one handler covers all of them, and the detail is written to be shown to a person.
Asking an assistant instead
This operation is also an MCP tool. Paste https://makehybrid.com/mcp/<your API key> into Claude, ChatGPT or any assistant that speaks MCP and ask for what you want in plain English — the assistant picks the call, fills in the ids and reads the answer back to you. There is nothing to install.
Which plan it is on
The Premium plan, on /premium. $9 per connected LinkedIn account per month, $7 from ten accounts and $5 from a thousand, with a 30-day trial covering one account.