POST/inbox/messages

Send a LinkedIn DM to an existing campaign lead (synchronous).

POST /inbox/messages
X-API-Key: sk_live_...
Content-Type: application/json

{
  "campaignId": "search_abc",
  "leadId": "lead_xyz",
  "text": "Hi Jane — following up on our conversation.",
  "accountId": "acc_abc"
}

Field	Required	Notes
`campaignId`	Yes
`leadId`	Yes
`text`	Yes	Max 8000 chars
`accountId`	No	Defaults from lead / product rules when omitted

{
  "ok": true,
  "chatId": "chat_...",
  "messageId": "msg_..."
}

Error code	When
`validation_error`	Missing/invalid fields
`not_found`	Campaign / lead
`account_disconnected`	Account not usable
`rate_limited` / `linkedin_daily_quota`	Caps
`send_failed`	Send failed

Sending may hand the conversation to human/agent rules as in the product inbox.