Realtime API (Preview) reference

The Realtime API is a WebSocket-based API that allows you to interact with the Azure OpenAI service in real-time.

The Realtime API (via /realtime) is built on the WebSockets API to facilitate fully asynchronous streaming communication between the end user and model. Device details like capturing and rendering audio data are outside the scope of the Realtime API. It should be used in the context of a trusted, intermediate service that manages both connections to end users and model endpoint connections. Don't use it directly from untrusted end user devices.

Connection

The Realtime API requires an existing Azure OpenAI resource endpoint in a supported region. The API is accessed via a secure WebSocket connection to the /realtime endpoint of your Azure OpenAI resource.

You can construct a full request URI by concatenating:

• The secure WebSocket (wss://) protocol
• Your Azure OpenAI resource endpoint hostname, for example, my-aoai-resource.openai.azure.com
• The openai/realtime API path
• An api-version query string parameter for a supported API version such as 2024-10-01-preview
• A deployment query string parameter with the name of your gpt-4o-realtime-preview model deployment

The following example is a well-constructed /realtime request URI:

wss://my-eastus2-openai-resource.openai.azure.com/openai/realtime?api-version=2024-10-01-preview&deployment=gpt-4o-realtime-preview-1001

Authentication

To authenticate:

• Microsoft Entra (recommended): Use token-based authentication with the /realtime API for an Azure OpenAI Service resource with managed identity enabled. Apply a retrieved authentication token using a Bearer token with the Authorization header.
• API key: An api-key can be provided in one of two ways:
  • Using an api-key connection header on the prehandshake connection. This option isn't available in a browser environment.
  • Using an api-key query string parameter on the request URI. Query string parameters are encrypted when using https/wss.

Client events

There are nine client events that can be sent from the client to the server:

Event	Description
RealtimeClientEventConversationItemCreate	The client conversation.item.create event is used to add a new item to the conversation's context, including messages, function calls, and function call responses.
RealtimeClientEventConversationItemDelete	The client conversation.item.delete event is used to remove an item from the conversation history.
RealtimeClientEventConversationItemTruncate	The client conversation.item.truncate event is used to truncate a previous assistant message's audio.
RealtimeClientEventInputAudioBufferAppend	The client input_audio_buffer.append event is used to append audio bytes to the input audio buffer.
RealtimeClientEventInputAudioBufferClear	The client input_audio_buffer.clear event is used to clear the audio bytes in the buffer.
RealtimeClientEventInputAudioBufferCommit	The client input_audio_buffer.commit event is used to commit the user input audio buffer.
RealtimeClientEventResponseCancel	The client response.cancel event is used to cancel an in-progress response.
RealtimeClientEventResponseCreate	The client response.create event is used to instruct the server to create a response via model inferencing.
RealtimeClientEventSessionUpdate	The client session.update event is used to update the session's default configuration.

RealtimeClientEventConversationItemCreate

The client conversation.item.create event is used to add a new item to the conversation's context, including messages, function calls, and function call responses. This event can be used to populate a history of the conversation and to add new items mid-stream. Currently this event can't populate assistant audio messages.

If successful, the server responds with a conversation.item.created event, otherwise an error event is sent.

Event structure

{
  "type": "conversation.item.create",
  "previous_item_id": "<previous_item_id>"
}

Properties

Field	Type	Description
type	string	The event type must be conversation.item.create.
previous_item_id	string	The ID of the preceding item after which the new item is inserted. If not set, the new item is appended to the end of the conversation. If set, it allows an item to be inserted mid-conversation. If the ID can't be found, then an error is returned and the item isn't added.
item	RealtimeConversationRequestItem	The item to add to the conversation.

RealtimeClientEventConversationItemDelete

The client conversation.item.delete event is used to remove an item from the conversation history.

The server responds with a conversation.item.deleted event, unless the item doesn't exist in the conversation history, in which case the server responds with an error.

Event structure

{
  "type": "conversation.item.delete",
  "item_id": "<item_id>"
}

Properties

Field	Type	Description
type	string	The event type must be conversation.item.delete.
item_id	string	The ID of the item to delete.

RealtimeClientEventConversationItemTruncate

The client conversation.item.truncate event is used to truncate a previous assistant message's audio. The server produces audio faster than realtime, so this event is useful when the user interrupts to truncate audio that was sent to the client but not yet played. The server's understanding of the audio with the client's playback is synchronized.

Truncating audio deletes the server-side text transcript to ensure there isn't text in the context that the user doesn't know about.

If the client event is successful, the server responds with a conversation.item.truncated event.

Event structure

{
  "type": "conversation.item.truncate",
  "item_id": "<item_id>",
  "content_index": 0,
  "audio_end_ms": 0
}

Properties

Field	Type	Description
type	string	The event type must be conversation.item.truncate.
item_id	string	The ID of the assistant message item to truncate. Only assistant message items can be truncated.
content_index	integer	The index of the content part to truncate. Set this property to "0".
audio_end_ms	integer	Inclusive duration up to which audio is truncated, in milliseconds. If the audio_end_ms is greater than the actual audio duration, the server responds with an error.

RealtimeClientEventInputAudioBufferAppend

The client input_audio_buffer.append event is used to append audio bytes to the input audio buffer. The audio buffer is temporary storage you can write to and later commit.

In Server VAD (Voice Activity Detection) mode, the audio buffer is used to detect speech and the server decides when to commit. When server VAD is disabled, the client can choose how much audio to place in each event up to a maximum of 15 MiB. For example, streaming smaller chunks from the client can allow the VAD to be more responsive.

Unlike most other client events, the server doesn't send a confirmation response to client input_audio_buffer.append event.

Event structure

{
  "type": "input_audio_buffer.append",
  "audio": "<audio>"
}

Properties

Field	Type	Description
type	string	The event type must be input_audio_buffer.append.
audio	string	Base64-encoded audio bytes. This value must be in the format specified by the input_audio_format field in the session configuration.

RealtimeClientEventInputAudioBufferClear

The client input_audio_buffer.clear event is used to clear the audio bytes in the buffer.

The server responds with an input_audio_buffer.cleared event.

Event structure

{
  "type": "input_audio_buffer.clear"
}

Properties

Field	Type	Description
type	string	The event type must be input_audio_buffer.clear.

RealtimeClientEventInputAudioBufferCommit

The client input_audio_buffer.commit event is used to commit the user input audio buffer, which creates a new user message item in the conversation. Audio is transcribed if input_audio_transcription is configured for the session.

When in server VAD mode, the client doesn't need to send this event, the server commits the audio buffer automatically. Without server VAD, the client must commit the audio buffer to create a user message item. This client event produces an error if the input audio buffer is empty.

Committing the input audio buffer doesn't create a response from the model.

The server responds with an input_audio_buffer.committed event.

Event structure

{
  "type": "input_audio_buffer.commit"
}

Properties

Field	Type	Description
type	string	The event type must be input_audio_buffer.commit.

RealtimeClientEventResponseCancel

The client response.cancel event is used to cancel an in-progress response.

The server responds with a response.cancelled event or an error if there's no response to cancel.

Event structure

{
  "type": "response.cancel"
}

Properties

Field	Type	Description
type	string	The event type must be response.cancel.

RealtimeClientEventResponseCreate

The client response.create event is used to instruct the server to create a response via model inferencing. When the session is configured in server VAD mode, the server creates responses automatically.

A response includes at least one item, and can have two, in which case the second is a function call. These items are appended to the conversation history.

The server responds with a response.created event, one or more item and content events (such as conversation.item.created and response.content_part.added), and finally a response.done event to indicate the response is complete.

Event structure

{
  "type": "response.create"
}

Properties

Field	Type	Description
type	string	The event type must be response.create.
response	RealtimeResponseOptions	The response options.

RealtimeClientEventSessionUpdate

The client session.update event is used to update the session's default configuration. The client can send this event at any time to update the session configuration, and any field can be updated at any time, except for voice.

Only fields that are present are updated. To clear a field (such as instructions), pass an empty string.

The server responds with a session.updated event that contains the full effective configuration.

Event structure

{
  "type": "session.update"
}

Properties

Field	Type	Description
type	string	The event type must be session.update.
session	RealtimeRequestSession	The session configuration.

Server events

There are 28 server events that can be received from the server:

Event	Description
RealtimeServerEventConversationCreated	The server conversation.created event is returned right after session creation. One conversation is created per session.
RealtimeServerEventConversationItemCreated	The server conversation.item.created event is returned when a conversation item is created.
RealtimeServerEventConversationItemDeleted	The server conversation.item.deleted event is returned when the client deleted an item in the conversation with a conversation.item.delete event.
RealtimeServerEventConversationItemInputAudioTranscriptionCompleted	The server conversation.item.input_audio_transcription.completed event is the result of audio transcription for speech written to the audio buffer.
RealtimeServerEventConversationItemInputAudioTranscriptionFailed	The server conversation.item.input_audio_transcription.failed event is returned when input audio transcription is configured, and a transcription request for a user message failed.
RealtimeServerEventConversationItemTruncated	The server conversation.item.truncated event is returned when the client truncates an earlier assistant audio message item with a conversation.item.truncate event.
RealtimeServerEventError	The server error event is returned when an error occurs, which could be a client problem or a server problem.
RealtimeServerEventInputAudioBufferCleared	The server input_audio_buffer.cleared event is returned when the client clears the input audio buffer with a input_audio_buffer.clear event.
RealtimeServerEventInputAudioBufferCommitted	The server input_audio_buffer.committed event is returned when an input audio buffer is committed, either by the client or automatically in server VAD mode.
RealtimeServerEventInputAudioBufferSpeechStarted	The server input_audio_buffer.speech_started event is returned in server_vad mode when speech is detected in the audio buffer.
RealtimeServerEventInputAudioBufferSpeechStopped	The server input_audio_buffer.speech_stopped event is returned in server_vad mode when the server detects the end of speech in the audio buffer.
RealtimeServerEventRateLimitsUpdated	The server rate_limits.updated event is emitted at the beginning of a response to indicate the updated rate limits.
RealtimeServerEventResponseAudioDelta	The server response.audio.delta event is returned when the model-generated audio is updated.
RealtimeServerEventResponseAudioDone	The server response.audio.done event is returned when the model-generated audio is done.
RealtimeServerEventResponseAudioTranscriptDelta	The server response.audio_transcript.delta event is returned when the model-generated transcription of audio output is updated.
RealtimeServerEventResponseAudioTranscriptDone	The server response.audio_transcript.done event is returned when the model-generated transcription of audio output is done streaming.
RealtimeServerEventResponseContentPartAdded	The server response.content_part.added event is returned when a new content part is added to an assistant message item.
RealtimeServerEventResponseContentPartDone	The server response.content_part.done event is returned when a content part is done streaming.
RealtimeServerEventResponseCreated	The server response.created event is returned when a new response is created. This is the first event of response creation, where the response is in an initial state of in_progress.
RealtimeServerEventResponseDone	The server response.done event is returned when a response is done streaming.
RealtimeServerEventResponseFunctionCallArgumentsDelta	The server response.function_call_arguments.delta event is returned when the model-generated function call arguments are updated.
RealtimeServerEventResponseFunctionCallArgumentsDone	The server response.function_call_arguments.done event is returned when the model-generated function call arguments are done streaming.
RealtimeServerEventResponseOutputItemAdded	The server response.output_item.added event is returned when a new item is created during response generation.
RealtimeServerEventResponseOutputItemDone	The server response.output_item.done event is returned when an item is done streaming.
RealtimeServerEventResponseTextDelta	The server response.text.delta event is returned when the model-generated text is updated.
RealtimeServerEventResponseTextDone	The server response.text.done event is returned when the model-generated text is done streaming.
RealtimeServerEventSessionCreated	The server session.created event is the first server event when you establish a new connection to the Realtime API. This event creates and returns a new session with the default session configuration.
RealtimeServerEventSessionUpdated	The server session.updated event is returned when a session is updated by the client. If there's an error, the server sends an error event instead.

RealtimeServerEventConversationCreated

The server conversation.created event is returned right after session creation. One conversation is created per session.

Event structure

{
  "type": "conversation.created",
  "conversation": {
    "id": "<id>",
    "object": "<object>"
  }
}

Properties

Field	Type	Description
type	string	The event type must be conversation.created.
conversation	object	The conversation resource.

Conversation properties

Field	Type	Description
id	string	The unique ID of the conversation.
object	string	The object type must be realtime.conversation.

RealtimeServerEventConversationItemCreated

The server conversation.item.created event is returned when a conversation item is created. There are several scenarios that produce this event:

• The server is generating a response, which if successful produces either one or two items, which is of type message (role assistant) or type function_call.
• The input audio buffer is committed, either by the client or the server (in server_vad mode). The server takes the content of the input audio buffer and adds it to a new user message item.
• The client sent a conversation.item.create event to add a new item to the conversation.

Event structure

{
  "type": "conversation.item.created",
  "previous_item_id": "<previous_item_id>"
}

Properties

Field	Type	Description
type	string	The event type must be conversation.item.created.
previous_item_id	string	The ID of the preceding item in the conversation context, allows the client to understand the order of the conversation.
item	RealtimeConversationResponseItem	The item that was created.

RealtimeServerEventConversationItemDeleted

The server conversation.item.deleted event is returned when the client deleted an item in the conversation with a conversation.item.delete event. This event is used to synchronize the server's understanding of the conversation history with the client's view.

Event structure

{
  "type": "conversation.item.deleted",
  "item_id": "<item_id>"
}

Properties

Field	Type	Description
type	string	The event type must be conversation.item.deleted.
item_id	string	The ID of the item that was deleted.

RealtimeServerEventConversationItemInputAudioTranscriptionCompleted

The server conversation.item.input_audio_transcription.completed event is the result of audio transcription for speech written to the audio buffer.

Transcription begins when the input audio buffer is committed by the client or server (in server_vad mode). Transcription runs asynchronously with response creation, so this event can come before or after the response events.

Realtime API models accept audio natively, and thus input transcription is a separate process run on a separate speech recognition model, currently always whisper-1. Thus the transcript can diverge somewhat from the model's interpretation, and should be treated as a rough guide.

Event structure

{
  "type": "conversation.item.input_audio_transcription.completed",
  "item_id": "<item_id>",
  "content_index": 0,
  "transcript": "<transcript>"
}

Properties

Field	Type	Description
type	string	The event type must be conversation.item.input_audio_transcription.completed.
item_id	string	The ID of the user message item containing the audio.
content_index	integer	The index of the content part containing the audio.
transcript	string	The transcribed text.

RealtimeServerEventConversationItemInputAudioTranscriptionFailed

The server conversation.item.input_audio_transcription.failed event is returned when input audio transcription is configured, and a transcription request for a user message failed. This event is separate from other error events so that the client can identify the related item.

Event structure

{
  "type": "conversation.item.input_audio_transcription.failed",
  "item_id": "<item_id>",
  "content_index": 0,
  "error": {
    "code": "<code>",
    "message": "<message>",
    "param": "<param>"
  }
}

Properties

Field	Type	Description
type	string	The event type must be conversation.item.input_audio_transcription.failed.
item_id	string	The ID of the user message item.
content_index	integer	The index of the content part containing the audio.
error	object	Details of the transcription error. See nested properties in the next table.

Error properties

Field	Type	Description
type	string	The type of error.
code	string	Error code, if any.
message	string	A human-readable error message.
param	string	Parameter related to the error, if any.

RealtimeServerEventConversationItemTruncated

The server conversation.item.truncated event is returned when the client truncates an earlier assistant audio message item with a conversation.item.truncate event. This event is used to synchronize the server's understanding of the audio with the client's playback.

This event truncates the audio and removes the server-side text transcript to ensure there's no text in the context that the user doesn't know about.

Event structure

{
  "type": "conversation.item.truncated",
  "item_id": "<item_id>",
  "content_index": 0,
  "audio_end_ms": 0
}

Properties

Field	Type	Description
type	string	The event type must be conversation.item.truncated.
item_id	string	The ID of the assistant message item that was truncated.
content_index	integer	The index of the content part that was truncated.
audio_end_ms	integer	The duration up to which the audio was truncated, in milliseconds.

RealtimeServerEventError

The server error event is returned when an error occurs, which could be a client problem or a server problem. Most errors are recoverable and the session stays open.

Event structure

{
  "type": "error",
  "error": {
    "code": "<code>",
    "message": "<message>",
    "param": "<param>",
    "event_id": "<event_id>"
  }
}

Properties

Field	Type	Description
type	string	The event type must be error.
error	object	Details of the error. See nested properties in the next table.

Error properties

Field	Type	Description
type	string	The type of error. For example, "invalid_request_error" and "server_error" are error types.
code	string	Error code, if any.
message	string	A human-readable error message.
param	string	Parameter related to the error, if any.
event_id	string	The ID of the client event that caused the error, if applicable.

RealtimeServerEventInputAudioBufferCleared

The server input_audio_buffer.cleared event is returned when the client clears the input audio buffer with a input_audio_buffer.clear event.

Event structure

{
  "type": "input_audio_buffer.cleared"
}

Properties

Field	Type	Description
type	string	The event type must be input_audio_buffer.cleared.

RealtimeServerEventInputAudioBufferCommitted

The server input_audio_buffer.committed event is returned when an input audio buffer is committed, either by the client or automatically in server VAD mode. The item_id property is the ID of the user message item created. Thus a conversation.item.created event is also sent to the client.

Event structure

{
  "type": "input_audio_buffer.committed",
  "previous_item_id": "<previous_item_id>",
  "item_id": "<item_id>"
}

Properties

Field	Type	Description
type	string	The event type must be input_audio_buffer.committed.
previous_item_id	string	The ID of the preceding item after which the new item is inserted.
item_id	string	The ID of the user message item created.

RealtimeServerEventInputAudioBufferSpeechStarted

The server input_audio_buffer.speech_started event is returned in server_vad mode when speech is detected in the audio buffer. This event can happen any time audio is added to the buffer (unless speech is already detected).

The client should expect to receive a input_audio_buffer.speech_stopped event when speech stops. The item_id property is the ID of the user message item created when speech stops. The item_id is also included in the input_audio_buffer.speech_stopped event unless the client manually commits the audio buffer during VAD activation.

Event structure

{
  "type": "input_audio_buffer.speech_started",
  "audio_start_ms": 0,
  "item_id": "<item_id>"
}

Properties

Field	Type	Description
type	string	The event type must be input_audio_buffer.speech_started.
audio_start_ms	integer	Milliseconds from the start of all audio written to the buffer during the session when speech was first detected. This property corresponds to the beginning of audio sent to the model, and thus includes the prefix_padding_ms configured in the session.
item_id	string	The ID of the user message item created when speech stops.

RealtimeServerEventInputAudioBufferSpeechStopped

The server input_audio_buffer.speech_stopped event is returned in server_vad mode when the server detects the end of speech in the audio buffer.

The server also sends a conversation.item.created event with the user message item created from the audio buffer.

Event structure

{
  "type": "input_audio_buffer.speech_stopped",
  "audio_end_ms": 0,
  "item_id": "<item_id>"
}

Properties

Field	Type	Description
type	string	The event type must be input_audio_buffer.speech_stopped.
audio_end_ms	integer	Milliseconds since the session started when speech stopped. This property corresponds to the end of audio sent to the model, and thus includes the min_silence_duration_ms configured in the session.
item_id	string	The ID of the user message item created.

RealtimeServerEventRateLimitsUpdated

The server rate_limits.updated event is emitted at the beginning of a response to indicate the updated rate limits.

When a response is created, some tokens are reserved for the output tokens. The rate limits shown here reflect that reservation, which is then adjusted accordingly once the response is completed.

Event structure

{
  "type": "rate_limits.updated",
  "rate_limits": [
    {
      "name": "<name>",
      "limit": 0,
      "remaining": 0,
      "reset_seconds": 0
    }
  ]
}

Properties

Field	Type	Description
type	string	The event type must be rate_limits.updated.
rate_limits	array of RealtimeServerEventRateLimitsUpdatedRateLimitsItem	The list of rate limit information.

RealtimeServerEventResponseAudioDelta

The server response.audio.delta event is returned when the model-generated audio is updated.

Event structure

{
  "type": "response.audio.delta",
  "response_id": "<response_id>",
  "item_id": "<item_id>",
  "output_index": 0,
  "content_index": 0,
  "delta": "<delta>"
}

Properties

Field	Type	Description
type	string	The event type must be response.audio.delta.
response_id	string	The ID of the response.
item_id	string	The ID of the item.
output_index	integer	The index of the output item in the response.
content_index	integer	The index of the content part in the item's content array.
delta	string	Base64-encoded audio data delta.

RealtimeServerEventResponseAudioDone

The server response.audio.done event is returned when the model-generated audio is done.

This event is also returned when a response is interrupted, incomplete, or canceled.

Event structure

{
  "type": "response.audio.done",
  "response_id": "<response_id>",
  "item_id": "<item_id>",
  "output_index": 0,
  "content_index": 0
}

Properties

Field	Type	Description
type	string	The event type must be response.audio.done.
response_id	string	The ID of the response.
item_id	string	The ID of the item.
output_index	integer	The index of the output item in the response.
content_index	integer	The index of the content part in the item's content array.

RealtimeServerEventResponseAudioTranscriptDelta

The server response.audio_transcript.delta event is returned when the model-generated transcription of audio output is updated.

Event structure

{
  "type": "response.audio_transcript.delta",
  "response_id": "<response_id>",
  "item_id": "<item_id>",
  "output_index": 0,
  "content_index": 0,
  "delta": "<delta>"
}

Properties

Field	Type	Description
type	string	The event type must be response.audio_transcript.delta.
response_id	string	The ID of the response.
item_id	string	The ID of the item.
output_index	integer	The index of the output item in the response.
content_index	integer	The index of the content part in the item's content array.
delta	string	The transcript delta.

RealtimeServerEventResponseAudioTranscriptDone

The server response.audio_transcript.done event is returned when the model-generated transcription of audio output is done streaming.

This event is also returned when a response is interrupted, incomplete, or canceled.

Event structure

{
  "type": "response.audio_transcript.done",
  "response_id": "<response_id>",
  "item_id": "<item_id>",
  "output_index": 0,
  "content_index": 0,
  "transcript": "<transcript>"
}

Properties

Field	Type	Description
type	string	The event type must be response.audio_transcript.done.
response_id	string	The ID of the response.
item_id	string	The ID of the item.
output_index	integer	The index of the output item in the response.
content_index	integer	The index of the content part in the item's content array.
transcript	string	The final transcript of the audio.

RealtimeServerEventResponseContentPartAdded

The server response.content_part.added event is returned when a new content part is added to an assistant message item during response generation.

Event structure

{
  "type": "response.content_part.added",
  "response_id": "<response_id>",
  "item_id": "<item_id>",
  "output_index": 0,
  "content_index": 0
}

Properties

Field	Type	Description
type	string	The event type must be response.content_part.added.
response_id	string	The ID of the response.
item_id	string	The ID of the item to which the content part was added.
output_index	integer	The index of the output item in the response.
content_index	integer	The index of the content part in the item's content array.
part	RealtimeContentPart	The content part that was added.

Part properties

Field	Type	Description
type	RealtimeContentPartType

RealtimeServerEventResponseContentPartDone

The server response.content_part.done event is returned when a content part is done streaming in an assistant message item.

This event is also returned when a response is interrupted, incomplete, or canceled.

Event structure

{
  "type": "response.content_part.done",
  "response_id": "<response_id>",
  "item_id": "<item_id>",
  "output_index": 0,
  "content_index": 0
}

Properties

Field	Type	Description
type	string	The event type must be response.content_part.done.
response_id	string	The ID of the response.
item_id	string	The ID of the item.
output_index	integer	The index of the output item in the response.
content_index	integer	The index of the content part in the item's content array.
part	RealtimeContentPart	The content part that is done.

Part properties

Field	Type	Description
type	RealtimeContentPartType

RealtimeServerEventResponseCreated

The server response.created event is returned when a new response is created. This is the first event of response creation, where the response is in an initial state of in_progress.

Event structure

{
  "type": "response.created"
}

Properties

Field	Type	Description
type	string	The event type must be response.created.
response	RealtimeResponse	The response object.

RealtimeServerEventResponseDone

The server response.done event is returned when a response is done streaming. This event is always emitted, no matter the final state. The response object included in the response.done event includes all output items in the response, but omits the raw audio data.

Event structure

{
  "type": "response.done"
}

Properties

Field	Type	Description
type	string	The event type must be response.done.
response	RealtimeResponse	The response object.

RealtimeServerEventResponseFunctionCallArgumentsDelta

The server response.function_call_arguments.delta event is returned when the model-generated function call arguments are updated.

Event structure

{
  "type": "response.function_call_arguments.delta",
  "response_id": "<response_id>",
  "item_id": "<item_id>",
  "output_index": 0,
  "call_id": "<call_id>",
  "delta": "<delta>"
}

Properties

Field	Type	Description
type	string	The event type must be response.function_call_arguments.delta.
response_id	string	The ID of the response.
item_id	string	The ID of the function call item.
output_index	integer	The index of the output item in the response.
call_id	string	The ID of the function call.
delta	string	The arguments delta as a JSON string.

RealtimeServerEventResponseFunctionCallArgumentsDone

The server response.function_call_arguments.done event is returned when the model-generated function call arguments are done streaming.

This event is also returned when a response is interrupted, incomplete, or canceled.

Event structure

{
  "type": "response.function_call_arguments.done",
  "response_id": "<response_id>",
  "item_id": "<item_id>",
  "output_index": 0,
  "call_id": "<call_id>",
  "arguments": "<arguments>"
}

Properties

Field	Type	Description
type	string	The event type must be response.function_call_arguments.done.
response_id	string	The ID of the response.
item_id	string	The ID of the function call item.
output_index	integer	The index of the output item in the response.
call_id	string	The ID of the function call.
arguments	string	The final arguments as a JSON string.

RealtimeServerEventResponseOutputItemAdded

The server response.output_item.added event is returned when a new item is created during response generation.

Event structure

{
  "type": "response.output_item.added",
  "response_id": "<response_id>",
  "output_index": 0
}

Properties

Field	Type	Description
type	string	The event type must be response.output_item.added.
response_id	string	The ID of the response to which the item belongs.
output_index	integer	The index of the output item in the response.
item	RealtimeConversationResponseItem	The item that was added.

RealtimeServerEventResponseOutputItemDone

The server response.output_item.done event is returned when an item is done streaming.

This event is also returned when a response is interrupted, incomplete, or canceled.

Event structure

{
  "type": "response.output_item.done",
  "response_id": "<response_id>",
  "output_index": 0
}

Properties

Field	Type	Description
type	string	The event type must be response.output_item.done.
response_id	string	The ID of the response to which the item belongs.
output_index	integer	The index of the output item in the response.
item	RealtimeConversationResponseItem	The item that is done streaming.

RealtimeServerEventResponseTextDelta

The server response.text.delta event is returned when the model-generated text is updated. The text corresponds to the text content part of an assistant message item.

Event structure

{
  "type": "response.text.delta",
  "response_id": "<response_id>",
  "item_id": "<item_id>",
  "output_index": 0,
  "content_index": 0,
  "delta": "<delta>"
}

Properties

Field	Type	Description
type	string	The event type must be response.text.delta.
response_id	string	The ID of the response.
item_id	string	The ID of the item.
output_index	integer	The index of the output item in the response.
content_index	integer	The index of the content part in the item's content array.
delta	string	The text delta.

RealtimeServerEventResponseTextDone

The server response.text.done event is returned when the model-generated text is done streaming. The text corresponds to the text content part of an assistant message item.

This event is also returned when a response is interrupted, incomplete, or canceled.

Event structure

{
  "type": "response.text.done",
  "response_id": "<response_id>",
  "item_id": "<item_id>",
  "output_index": 0,
  "content_index": 0,
  "text": "<text>"
}

Properties

Field	Type	Description
type	string	The event type must be response.text.done.
response_id	string	The ID of the response.
item_id	string	The ID of the item.
output_index	integer	The index of the output item in the response.
content_index	integer	The index of the content part in the item's content array.
text	string	The final text content.

RealtimeServerEventSessionCreated

The server session.created event is the first server event when you establish a new connection to the Realtime API. This event creates and returns a new session with the default session configuration.

Event structure

{
  "type": "session.created"
}

Properties

Field	Type	Description
type	string	The event type must be session.created.
session	RealtimeResponseSession	The session object.

RealtimeServerEventSessionUpdated

The server session.updated event is returned when a session is updated by the client. If there's an error, the server sends an error event instead.

Event structure

{
  "type": "session.updated"
}

Properties

Field	Type	Description
type	string	The event type must be session.updated.
session	RealtimeResponseSession	The session object.

Components

RealtimeAudioFormat

Allowed Values:

• pcm16
• g711_ulaw
• g711_alaw

RealtimeAudioInputTranscriptionModel

Allowed Values:

• whisper-1

RealtimeAudioInputTranscriptionSettings

Field	Type	Description
model	RealtimeAudioInputTranscriptionModel	The default whisper-1 model is currently the only model supported for audio input transcription.

RealtimeClientEvent

Field	Type	Description
type	RealtimeClientEventType	The type of the client event.
event_id	string	The unique ID of the event. The ID can be specified by the client to help identify the event.

RealtimeClientEventType

Allowed Values:

• session.update
• input_audio_buffer.append
• input_audio_buffer.commit
• input_audio_buffer.clear
• conversation.item.create
• conversation.item.delete
• conversation.item.truncate
• response.create
• response.cancel

RealtimeContentPart

Field	Type	Description
type	RealtimeContentPartType	The type of the content part.

RealtimeContentPartType

Allowed Values:

• input_text
• input_audio
• text
• audio

RealtimeConversationItemBase

The item to add to the conversation.

RealtimeConversationRequestItem

You use the RealtimeConversationRequestItem object to create a new item in the conversation via the conversation.item.create event.

Field	Type	Description
type	RealtimeItemType	The type of the item.
id	string	The unique ID of the item. The ID can be specified by the client to help manage server-side context. If the client doesn't provide an ID, the server generates one.

RealtimeConversationResponseItem

The RealtimeConversationResponseItem object represents an item in the conversation. It's used in some of the server events, such as:

• conversation.item.created
• response.output_item.added
• response.output_item.done
• response.created (via the response property type RealtimeResponse)
• response.done (via the response property type RealtimeResponse)

Field	Type	Description
object	string	The identifier for the returned API object. Allowed values: realtime.item
type	RealtimeItemType	The type of the item. Allowed values: message, function_call, function_call_output
id	string	The unique ID of the item. The ID can be specified by the client to help manage server-side context. If the client doesn't provide an ID, the server generates one. This property is nullable.

RealtimeFunctionTool

The definition of a function tool as used by the realtime endpoint.

Field	Type	Description
type	string	The type of the tool. Allowed values: function
name	string	The name of the function.
description	string	The description of the function, including usage guidelines. For example, "Use this function to get the current time."
parameters	object	The parameters of the function in the form of a JSON object.

RealtimeItemStatus

Allowed Values:

• in_progress
• completed
• incomplete

RealtimeItemType

Allowed Values:

• message
• function_call
• function_call_output

RealtimeMessageRole

Allowed Values:

• system
• user
• assistant

RealtimeRequestAssistantMessageItem

Field	Type	Description
role	string	The role of the message. Allowed values: assistant
content	array of RealtimeRequestTextContentPart	The content of the message.

RealtimeRequestAudioContentPart

Field	Type	Description
type	string	The type of the content part. Allowed values: input_audio
transcript	string	The transcript of the audio.

RealtimeRequestFunctionCallItem

Field	Type	Description
type	string	The type of the item. Allowed values: function_call
name	string	The name of the function call item.
call_id	string	The ID of the function call item.
arguments	string	The arguments of the function call item.
status	RealtimeItemStatus	The status of the item.

RealtimeRequestFunctionCallOutputItem

Field	Type	Description
type	string	The type of the item. Allowed values: function_call_output
call_id	string	The ID of the function call item.
output	string	The output of the function call item.

RealtimeRequestMessageItem

Field	Type	Description
type	string	The type of the item. Allowed values: message
role	RealtimeMessageRole	The role of the message.
status	RealtimeItemStatus	The status of the item.

RealtimeRequestMessageReferenceItem

Field	Type	Description
type	string	The type of the item. Allowed values: message
id	string	The ID of the message item.

RealtimeRequestSession

You use the RealtimeRequestSession object when you want to update the session configuration via the session.update event.

Field	Type	Description
modalities	array	The modalities that the session supports. Allowed values: text, audio For example, "modalities": ["text", "audio"] is the default setting that enables both text and audio modalities. To enable only text, set "modalities": ["text"]. You can't enable only audio.
instructions	string	The instructions (the system message) to guide the model's text and audio responses. Here are some example instructions to help guide content and format of text and audio responses: "instructions": "be succinct" "instructions": "act friendly" "instructions": "here are examples of good responses" Here are some example instructions to help guide audio behavior: "instructions": "talk quickly" "instructions": "inject emotion into your voice" "instructions": "laugh frequently" While the model might not always follow these instructions, they provide guidance on the desired behavior.
voice	RealtimeVoice	The voice used for the model response for the session. Once the voice is used in the session for the model's audio response, it can't be changed.
input_audio_format	RealtimeAudioFormat	The format for the input audio.
output_audio_format	RealtimeAudioFormat	The format for the output audio.
input_audio_transcription	RealtimeAudioInputTranscriptionSettings	The settings for audio input transcription. This property is nullable.
turn_detection	RealtimeTurnDetection	The turn detection settings for the session. This property is nullable.
tools	array of RealtimeTool	The tools available to the model for the session.
tool_choice	RealtimeToolChoice	The tool choice for the session. Allowed values: auto, none, and required. Otherwise, you can specify the name of the function to use.
temperature	number	The sampling temperature for the model. The allowed temperature values are limited to [0.6, 1.2]. Defaults to 0.8.
max_response_output_tokens	integer or "inf"	The maximum number of output tokens per assistant response, inclusive of tool calls. Specify an integer between 1 and 4096 to limit the output tokens. Otherwise, set the value to "inf" to allow the maximum number of tokens. For example, to limit the output tokens to 1000, set "max_response_output_tokens": 1000. To allow the maximum number of tokens, set "max_response_output_tokens": "inf". Defaults to "inf".

RealtimeRequestSystemMessageItem

Field	Type	Description
role	string	The role of the message. Allowed values: system
content	array of RealtimeRequestTextContentPart	The content of the message.

RealtimeRequestTextContentPart

Field	Type	Description
type	string	The type of the content part. Allowed values: input_text
text	string	The text content.

RealtimeRequestUserMessageItem

Field	Type	Description
role	string	The role of the message. Allowed values: user
content	array of RealtimeRequestTextContentPart or RealtimeRequestAudioContentPart	The content of the message.

RealtimeResponse

Field	Type	Description
object	string	The response object. Allowed values: realtime.response
id	string	The unique ID of the response.
status	RealtimeResponseStatus	The status of the response. The default status value is in_progress.
status_details	RealtimeResponseStatusDetails	The details of the response status. This property is nullable.
output	array of RealtimeConversationResponseItem	The output items of the response.
usage	object	Usage statistics for the response. Each Realtime API session maintains a conversation context and appends new items to the conversation. Output from previous turns (text and audio tokens) is input for later turns. See nested properties next.
+ total_tokens	integer	The total number of tokens in the Response including input and output text and audio tokens. A property of the usage object.
+ input_tokens	integer	The number of input tokens used in the response, including text and audio tokens. A property of the usage object.
+ output_tokens	integer	The number of output tokens sent in the response, including text and audio tokens. A property of the usage object.
+ input_token_details	object	Details about the input tokens used in the response. A property of the usage object. br> See nested properties next.
+ cached_tokens	integer	The number of cached tokens used in the response. A property of the input_token_details object.
+ text_tokens	integer	The number of text tokens used in the response. A property of the input_token_details object.
+ audio_tokens	integer	The number of audio tokens used in the response. A property of the input_token_details object.
+ output_token_details	object	Details about the output tokens used in the response. A property of the usage object. See nested properties next.
+ text_tokens	integer	The number of text tokens used in the response. A property of the output_token_details object.
+ audio_tokens	integer	The number of audio tokens used in the response. A property of the output_token_details object.

RealtimeResponseAudioContentPart

Field	Type	Description
type	string	The type of the content part. Allowed values: audio
transcript	string	The transcript of the audio. This property is nullable.

RealtimeResponseBase

The response resource.

RealtimeResponseFunctionCallItem

Field	Type	Description
type	string	The type of the item. Allowed values: function_call
name	string	The name of the function call item.
call_id	string	The ID of the function call item.
arguments	string	The arguments of the function call item.
status	RealtimeItemStatus	The status of the item.

RealtimeResponseFunctionCallOutputItem

Field	Type	Description
type	string	The type of the item. Allowed values: function_call_output
call_id	string	The ID of the function call item.
output	string	The output of the function call item.

RealtimeResponseMessageItem

Field	Type	Description
type	string	The type of the item. Allowed values: message
role	RealtimeMessageRole	The role of the message.
content	array	The content of the message. Array items: RealtimeResponseTextContentPart
status	RealtimeItemStatus	The status of the item.

RealtimeResponseOptions

Field	Type	Description
modalities	array	The modalities that the session supports. Allowed values: text, audio For example, "modalities": ["text", "audio"] is the default setting that enables both text and audio modalities. To enable only text, set "modalities": ["text"]. You can't enable only audio.
instructions	string	The instructions (the system message) to guide the model's text and audio responses. Here are some example instructions to help guide content and format of text and audio responses: "instructions": "be succinct" "instructions": "act friendly" "instructions": "here are examples of good responses" Here are some example instructions to help guide audio behavior: "instructions": "talk quickly" "instructions": "inject emotion into your voice" "instructions": "laugh frequently" While the model might not always follow these instructions, they provide guidance on the desired behavior.
voice	RealtimeVoice	The voice used for the model response for the session. Once the voice is used in the session for the model's audio response, it can't be changed.
output_audio_format	RealtimeAudioFormat	The format for the output audio.
tools	array of RealtimeTool	The tools available to the model for the session.
tool_choice	RealtimeToolChoice	The tool choice for the session.
temperature	number	The sampling temperature for the model. The allowed temperature values are limited to [0.6, 1.2]. Defaults to 0.8.
max__output_tokens	integer or "inf"	The maximum number of output tokens per assistant response, inclusive of tool calls. Specify an integer between 1 and 4096 to limit the output tokens. Otherwise, set the value to "inf" to allow the maximum number of tokens. For example, to limit the output tokens to 1000, set "max_response_output_tokens": 1000. To allow the maximum number of tokens, set "max_response_output_tokens": "inf". Defaults to "inf".

RealtimeResponseSession

The RealtimeResponseSession object represents a session in the Realtime API. It's used in some of the server events, such as:

• session.created
• session.updated

Field	Type	Description
object	string	The session object. Allowed values: realtime.session
id	string	The unique ID of the session.
model	string	The model used for the session.
modalities	array	The modalities that the session supports. Allowed values: text, audio For example, "modalities": ["text", "audio"] is the default setting that enables both text and audio modalities. To enable only text, set "modalities": ["text"]. You can't enable only audio.
instructions	string	The instructions (the system message) to guide the model's text and audio responses. Here are some example instructions to help guide content and format of text and audio responses: "instructions": "be succinct" "instructions": "act friendly" "instructions": "here are examples of good responses" Here are some example instructions to help guide audio behavior: "instructions": "talk quickly" "instructions": "inject emotion into your voice" "instructions": "laugh frequently" While the model might not always follow these instructions, they provide guidance on the desired behavior.
voice	RealtimeVoice	The voice used for the model response for the session. Once the voice is used in the session for the model's audio response, it can't be changed.
input_audio_format	RealtimeAudioFormat	The format for the input audio.
output_audio_format	RealtimeAudioFormat	The format for the output audio.
input_audio_transcription	RealtimeAudioInputTranscriptionSettings	The settings for audio input transcription. This property is nullable.
turn_detection	RealtimeTurnDetection	The turn detection settings for the session. This property is nullable.
tools	array of RealtimeTool	The tools available to the model for the session.
tool_choice	RealtimeToolChoice	The tool choice for the session.
temperature	number	The sampling temperature for the model. The allowed temperature values are limited to [0.6, 1.2]. Defaults to 0.8.
max_response_output_tokens	integer or "inf"	The maximum number of output tokens per assistant response, inclusive of tool calls. Specify an integer between 1 and 4096 to limit the output tokens. Otherwise, set the value to "inf" to allow the maximum number of tokens. For example, to limit the output tokens to 1000, set "max_response_output_tokens": 1000. To allow the maximum number of tokens, set "max_response_output_tokens": "inf".

RealtimeResponseStatus

Allowed Values:

• in_progress
• completed
• cancelled
• incomplete
• failed

RealtimeResponseStatusDetails

Field	Type	Description
type	RealtimeResponseStatus	The status of the response.

RealtimeResponseTextContentPart

Field	Type	Description
type	string	The type of the content part. Allowed values: text
text	string	The text content.

RealtimeServerEvent

Field	Type	Description
type	RealtimeServerEventType	The type of the server event.
event_id	string	The unique ID of the server event.

RealtimeServerEventRateLimitsUpdatedRateLimitsItem

Field	Type	Description
name	string	The rate limit property name that this item includes information about.
limit	integer	The maximum configured limit for this rate limit property.
remaining	integer	The remaining quota available against the configured limit for this rate limit property.
reset_seconds	number	The remaining time, in seconds, until this rate limit property is reset.

RealtimeServerEventType

Allowed Values:

• session.created
• session.updated
• conversation.created
• conversation.item.created
• conversation.item.deleted
• conversation.item.truncated
• response.created
• response.done
• rate_limits.updated
• response.output_item.added
• response.output_item.done
• response.content_part.added
• response.content_part.done
• response.audio.delta
• response.audio.done
• response.audio_transcript.delta
• response.audio_transcript.done
• response.text.delta
• response.text.done
• response.function_call_arguments.delta
• response.function_call_arguments.done
• input_audio_buffer.speech_started
• input_audio_buffer.speech_stopped
• conversation.item.input_audio_transcription.completed
• conversation.item.input_audio_transcription.failed
• input_audio_buffer.committed
• input_audio_buffer.cleared
• error

RealtimeServerVadTurnDetection

Field	Type	Description
type	string	The type of turn detection. Allowed values: server_vad
threshold	number	The activation threshold for the server VAD turn detection. In noisy environments, you might need to increase the threshold to avoid false positives. In quiet environments, you might need to decrease the threshold to avoid false negatives. Defaults to 0.5. You can set the threshold to a value between 0.0 and 1.0.
prefix_padding_ms	string	The duration of speech audio (in milliseconds) to include before the start of detected speech. Defaults to 300.
silence_duration_ms	string	The duration of silence (in milliseconds) to detect the end of speech. You want to detect the end of speech as soon as possible, but not too soon to avoid cutting off the last part of the speech. The model will respond more quickly if you set this value to a lower number, but it might cut off the last part of the speech. If you set this value to a higher number, the model will wait longer to detect the end of speech, but it might take longer to respond.

RealtimeSessionBase

Realtime session object configuration.

RealtimeTool

The base representation of a realtime tool definition.

Field	Type	Description
type	RealtimeToolType	The type of the tool.

RealtimeToolChoice

The combined set of available representations for a realtime tool_choice parameter, encompassing both string literal options like 'auto' and structured references to defined tools.

RealtimeToolChoiceFunctionObject

The representation of a realtime tool_choice selecting a named function tool.

Field	Type	Description
type	string	The type of the tool_choice. Allowed values: function
function	object	The function tool to select. See nested properties next.
+ name	string	The name of the function tool. A property of the function object.

RealtimeToolChoiceLiteral

The available set of mode-level, string literal tool_choice options for the realtime endpoint.

Allowed Values:

• auto
• none
• required

RealtimeToolChoiceObject

A base representation for a realtime tool_choice selecting a named tool.

Field	Type	Description
type	RealtimeToolType	The type of the tool_choice.

RealtimeToolType

The supported tool type discriminators for realtime tools. Currently, only 'function' tools are supported.

Allowed Values:

• function

RealtimeTurnDetection

Field	Type	Description
type	RealtimeTurnDetectionType	The type of turn detection. Allowed values: server_vad

RealtimeTurnDetectionType

Allowed Values:

• server_vad

RealtimeVoice

Allowed Values:

• alloy
• shimmer
• echo

Related content

• Get started with the Realtime API quickstart.
• Learn more about How to use the Realtime API.