---
title: "Exchange WebRTC SDP for a conversation voice session"
method: POST
path: "/tally/voice/sessions/{sessionId}/webrtc"
tags: ["Tally Voice"]
---

# Exchange WebRTC SDP for a conversation voice session

`POST /tally/voice/sessions/{sessionId}/webrtc`

## Request

- Base URL: `https://ledgerhq.pro/api/v1`
- URL: `https://ledgerhq.pro/api/v1/tally/voice/sessions/{sessionId}/webrtc`
- Auth: one of:
  - HTTP bearer and API key in header `x-organization-id`
  - HTTP bearer and API key in header `x-organization-id`

Accepts the mobile client's local SDP offer and returns the OpenAI Realtime answer SDP. The OpenAI API key never leaves the server. Media is input-only (server VAD + transcription); spoken Tally replies use server TTS over the control gateway.

## Path parameters

- `sessionId` string, uuid, required

## Request body

- object
  - `sdp` string, required

## Response `200`

WebRTC answer SDP

- object
  - `sdp` string, required
  - `type` 'answer', required
  - `transport` 'webrtc', required

## Other responses

- `400`: Error response
- `404`: Error response
- `503`: Error response
- `default`: Error response

---

[API](https://skmtc.dev/ledgerhq-pro/apis/ledgerhq-bookkeeping-api.md) · [All operations](https://skmtc.dev/ledgerhq-pro/apis/ledgerhq-bookkeeping-api/llms.txt) · [OpenAPI document](https://skmtc.dev/ledgerhq-pro/apis/ledgerhq-bookkeeping-api/revisions/9a8269f0a586?raw)