## Accept call

**post** `/live/sessions/{session_id}/accept`

Accept an incoming SIP call. Supply session with type live, the model, and startup configuration. Before accepting calls, follow the [Live prompting guide](/api/docs/guides/live-prompting) to write frontend conversation instructions and a separate backend prompt. SIP media format is negotiated; omit audio.format.

### Path Parameters

- `session_id: string`

### Body Parameters

- `session: object { model, type, audio, 4 more }`

  Model and startup configuration for the Live session that answers the incoming SIP call.

  - `model: string or "gpt-live-1"`

    The Live model to use for the accepted call.

    - `string`

    - `"gpt-live-1"`

      The Live model. Required in the session configuration for every transport; do not pass it as a URL query parameter.

      - `"gpt-live-1"`

  - `type: "live"`

    The session type. Always `live`.

    - `"live"`

  - `audio: optional object { output }`

    Startup audio output configuration. SIP negotiates the media format; audio.format is only accepted for primary WebSockets. Voice cannot change after startup.

    - `output: optional object { voice }`

      Settings for speech generated by the Live model. Choose the voice before starting the session.

      - `voice: optional string or "alloy" or "ash" or "ballad" or 19 more or CustomVoice`

        The voice used for Live speech, as a built-in voice name or a custom voice object containing its ID. Defaults to `marin` and cannot change after startup.

        - `string`

        - `"alloy" or "ash" or "ballad" or 19 more`

          The voice used for Live speech, as a built-in voice name or a custom voice object containing its ID. Defaults to `marin` and cannot change after startup.

          - `"alloy"`

          - `"ash"`

          - `"ballad"`

          - `"beacon"`

          - `"bossa"`

          - `"cedar"`

          - `"cinder"`

          - `"coral"`

          - `"delta"`

          - `"echo"`

          - `"gleam"`

          - `"marin"`

          - `"meridian"`

          - `"quartz"`

          - `"ripple"`

          - `"sage"`

          - `"shimmer"`

          - `"stone"`

          - `"tempo"`

          - `"verse"`

          - `"vesper"`

          - `"willow"`

        - `CustomVoice object { id }`

          - `id: string`

  - `delegation: optional ClientDelegation or object { responses, type }  or null`

    Who handles tasks delegated by the Live model. Omitted or null selects your application; use `responses` to let the API manage a Responses backend.

    - `ClientDelegation object { type }`

      Delegate tasks to your application. The Live session emits delegation events that your backend handles.

      - `type: "client"`

        The delegation owner. Always `client` for tasks handled by your application.

        - `"client"`

    - `Responses object { responses, type }`

      Delegate tasks to a Responses model managed by the Live session.

      - `responses: ResponsesDelegationConfig`

        Backend model, prompt, and tools used when the Live session delegates a task to Responses.

        - `model: string`

          The model used for server-owned Responses delegations.

        - `instructions: optional string or null`

          Instructions for the delegated Responses model, separate from Live instructions. See [backend prompting](/api/docs/guides/live-delegation#start-with-your-existing-backend-prompt).

        - `max_output_tokens: optional number or null`

          Maximum number of output tokens for each delegated response.

        - `parallel_tool_calls: optional boolean or null`

          Whether the delegated Responses model may request multiple tool calls in a single response.

        - `reasoning: optional object { effort, summary }  or null`

          Reasoning settings passed to each delegated Responses request.

          - `effort: optional "none" or "minimal" or "low" or 3 more or null`

            How much reasoning effort the delegated Responses model should use. Supported values depend on the backend model.

            - `"none"`

            - `"minimal"`

            - `"low"`

            - `"medium"`

            - `"high"`

            - `"xhigh"`

          - `summary: optional "concise" or "detailed" or "auto" or null`

            The reasoning summary to request from the delegated Responses model, when supported.

            - `"concise"`

            - `"detailed"`

            - `"auto"`

        - `service_tier: optional "auto" or "default" or "fast_tier_temp_pilot" or 3 more or null`

          Service tier for delegated Responses requests.

          - `"auto"`

          - `"default"`

          - `"fast_tier_temp_pilot"`

          - `"flex"`

          - `"priority"`

          - `"ultrafast"`

        - `text: optional object { verbosity }  or null`

          Text generation settings passed to each delegated Responses request.

          - `verbosity: optional "low" or "medium" or "high" or null`

            The amount of detail in text generated by the Responses backend. This does not configure the Live model’s spoken delivery.

            - `"low"`

            - `"medium"`

            - `"high"`

        - `tool_choice: optional "auto" or "none" or "required" or object { name, type }  or object { name, server_label, type }`

          Controls which tool the Responses backend uses when handling a task delegated by the Live model.

          - `LiveToolChoiceEnum = "auto" or "none" or "required"`

            - `"auto"`

            - `"none"`

            - `"required"`

          - `LiveFunctionToolChoiceParam object { name, type }`

            - `name: string`

            - `type: "function"`

              - `"function"`

          - `LiveMCPToolChoiceParam object { name, server_label, type }`

            - `name: string`

            - `server_label: string`

            - `type: "mcp"`

              - `"mcp"`

        - `tools: optional array of FunctionTool or object { type }`

          Tools available to the Responses backend while it handles tasks delegated by the Live model.

          - `FunctionTool object { name, type, description, 2 more }`

            A function tool available to the Responses backend when the Live model delegates a task.

            - `name: string`

              The name the delegated Responses model uses when calling this function.

            - `type: "function"`

              The tool type. Always `function`.

              - `"function"`

            - `description: optional string or null`

              What the function does and when the delegated Responses model should call it.

            - `parameters: optional map[unknown] or null`

              A JSON Schema object describing the arguments accepted by the function.

            - `strict: optional boolean or null`

              Whether the delegated Responses model must follow the function’s parameter schema exactly.

          - `WebSearch object { type }`

            A web search tool available to the Live session’s Responses backend.

            - `type: "web_search"`

              The tool type. Always `web_search`.

              - `"web_search"`

      - `type: "responses"`

        The delegation owner. Always `responses` for tasks handled by the Responses API.

        - `"responses"`

  - `input: optional array of InitialItem`

    Ordered text-only history supplied before startup. Supports developer, user, and assistant messages with one text part each; at most 128 messages and 8,192 rendered tokens in total.

    - `Developer object { content, role, id, 2 more }`

      A developer message included in the initial text history of a Live session.

      - `content: array of object { text, type }`

        The message content. Supply exactly one text part for the initial Live conversation history.

        - `text: string`

          The message text to include in the Live session’s initial conversation history.

        - `type: optional "input_text"`

          The text content type. Always `input_text`.

          - `"input_text"`

      - `role: "developer"`

        The author of this history message. Always `developer`.

        - `"developer"`

      - `id: optional string or null`

        An optional identifier for the supplied history message. Live uses the message’s role and text to initialize the conversation.

      - `status: optional "incomplete" or "completed" or null`

        The supplied message’s status. Live uses its text as history and does not resume an incomplete message.

        - `"incomplete"`

        - `"completed"`

      - `type: optional "message"`

        The history item type. Always `message`.

        - `"message"`

    - `User object { content, role, id, 2 more }`

      A user message included in the initial text history of a Live session.

      - `content: array of object { text, type }`

        The message content. Supply exactly one text part for the initial Live conversation history.

        - `text: string`

          The message text to include in the Live session’s initial conversation history.

        - `type: optional "input_text"`

          The text content type. Always `input_text`.

          - `"input_text"`

      - `role: "user"`

        The author of this history message. Always `user`.

        - `"user"`

      - `id: optional string or null`

        An optional identifier for the supplied history message. Live uses the message’s role and text to initialize the conversation.

      - `status: optional "incomplete" or "completed" or null`

        The supplied message’s status. Live uses its text as history and does not resume an incomplete message.

        - `"incomplete"`

        - `"completed"`

      - `type: optional "message"`

        The history item type. Always `message`.

        - `"message"`

    - `Assistant object { content, role, id, 2 more }`

      An assistant message included in the initial text history of a Live session.

      - `content: array of object { text, type }  or object { text, type }`

        The message content. Supply exactly one text part for the initial Live conversation history.

        - `Text object { text, type }`

          Assistant text supplied as conversation history when starting a Live session.

          - `text: string`

            The message text to include in the Live session’s initial conversation history.

          - `type: optional "text"`

            The text content type. Always `text`.

            - `"text"`

        - `OutputText object { text, type }`

          Assistant output text supplied as conversation history when starting a Live session.

          - `text: string`

            The message text to include in the Live session’s initial conversation history.

          - `type: "output_text"`

            The text content type. Always `output_text`.

            - `"output_text"`

      - `role: "assistant"`

        The author of this history message. Always `assistant`.

        - `"assistant"`

      - `id: optional string or null`

        An optional identifier for the supplied history message. Live uses the message’s role and text to initialize the conversation.

      - `status: optional "incomplete" or "completed" or null`

        The supplied message’s status. Live uses its text as history and does not resume an incomplete message.

        - `"incomplete"`

        - `"completed"`

      - `type: optional "message"`

        The history item type. Always `message`.

        - `"message"`

  - `instructions: optional string or null`

    Frontend instructions for voice, conversation, interruptions, and when to delegate. Start with the [Live prompting guide](/api/docs/guides/live-prompting); put business rules and tool workflows in a separate [backend prompt](/api/docs/guides/live-delegation#start-with-your-existing-backend-prompt). Limited to 16,384 client-supplied tokens. Omitted or blank instructions use server defaults. Immutable after startup.

  - `store: optional boolean`

    Whether to store the session for later forking and recording download. Defaults to false for new sessions.

### Example

```http
curl https://api.openai.com/v1/live/sessions/$SESSION_ID/accept \
    -H 'Content-Type: application/json' \
    -H "Authorization: Bearer $OPENAI_API_KEY" \
    -d '{
          "session": {
            "model": "gpt-live-1",
            "type": "live"
          }
        }'
```