LinkedIn API endpoint

LinkedIn voice message API: recorded or AI-generated

Swarmhit's LinkedIn voice message API sends voice notes in two ways. Inside a conversation, POST /inbox/chats/{id}/messages takes an audio URL and transcodes it to LinkedIn's voice format on the server, up to about one minute. In campaigns, AI voice notes speak a written script for each lead, in one of Swarmhit's voices or a voice your workspace cloned, with an optional approval queue.

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Endpoints

POST/inbox/chats/{id}/messages
Send a voice message in a conversation
GET/voices
List the voices an AI voice note can use
GET/pending-voice-notes
List AI voice notes awaiting approval

POST

/inbox/chats/{id}/messages

api/v1

curl -X POST https://app.swarmhit.com/api/v1/inbox/chats/chat_456/messages \
  -H "Authorization: Bearer $SWARMHIT_API_KEY" \
  -H "Idempotency-Key: 6f1c2f3e-voice-ana" \
  -H "Content-Type: application/json" \
  -d '{
    "voiceMessage": { "url": "https://cdn.example.com/notes/ana.m4a", "durationMs": 31000 }
  }'

How the LinkedIn voice message API works

In a conversation, the voiceMessage audio is fetched from its URL and transcoded to LinkedIn's voice note format on the server, up to about one minute.
AI voice notes in campaigns list their drafts through GET /pending-voice-notes: audioUrl plays exactly what the lead would hear and script shows what it says. Approve, reject or regenerate each one, and a voice_note.pending webhook tells your product when one is waiting.
GET /voices returns the shared voice library plus the voices your workspace cloned.

As a campaign step

The same action runs inside sequences as the voice_note and ai_voice_note steps: one POST /campaigns sets up the whole sequence, and the engine schedules each step per sender and mailbox, inside the sending window, with rotation across senders.

voice_note sends a recording made once (m4a/AAC), the same for every lead, or one recording per sender with voiceAssignments.
ai_voice_note speaks a script and fallbackScript of up to 800 characters, about a minute of audio, with {{variables}} so every note is personal. Generation draws the workspace's credits, identical scripts are generated once and reused, and requireApproval holds each note for a listen before it goes out.

Limits and safety

Voice notes are LinkedIn messages: they go to connections, through the conversation or the campaign, from the sender's own account.
Every sender runs on its own dedicated proxy with managed warmup and health checks, behind 250+ safeguards monitored 24/7.

LinkedIn senders cost $16.90 a month each for the first 50, tiered down to $6.90, with no minimum. See pricing.

Webhooks

Events to subscribe to: voice_note.pending, message.sent, message.received. Deliveries are signed and retried. How LinkedIn webhooks work

LinkedIn voice message API, answered

Can you send LinkedIn voice messages through an API?

Yes. Swarmhit sends voice notes inside conversations from an audio URL, transcoded to LinkedIn's format on the server, and campaigns can send a recorded note or AI voice notes generated per lead. LinkedIn's official APIs do not offer this for outreach.

Can the voice notes use my own voice?

Yes. A workspace can clone a voice and use it for AI voice notes, and campaigns can assign a different voice per sender. Each generated note speaks the lead's own variables from a script of up to 800 characters.

How long can a LinkedIn voice note be?

About one minute. Voice messages sent in conversations are capped at roughly a minute, and AI voice note scripts are capped at 800 characters, which is about a minute of speech.

Can I check AI voice notes before they are sent?

Yes. With requireApproval on, each generated note waits in a queue. GET /pending-voice-notes returns an audioUrl that plays exactly what the lead will hear, plus the script, and you approve, reject or regenerate it.