> ## Documentation Index > Fetch the complete documentation index at: https://openai-hd4n6.mintlify.site/llms.txt > Use this file to discover all available pages before exploring further. # Create session > Create an ephemeral API token for use in client-side applications with the Realtime API. Can be configured with the same session parameters as the `session.update` client event. It responds with a session object, plus a `client_secret` key which contains a usable ephemeral API token that can be used to authenticate browser clients for the Realtime API. ## OpenAPI ````yaml api-definition.yaml post /realtime/sessions openapi: 3.0.0 info: title: OpenAI API description: >- The OpenAI REST API. Please see https://platform.openai.com/docs/api-reference for more details. version: 2.3.0 termsOfService: https://openai.com/policies/terms-of-use contact: name: OpenAI Support url: https://help.openai.com/ license: name: MIT url: https://github.com/openai/openai-openapi/blob/master/LICENSE servers: - url: https://api.openai.com/v1 security: - ApiKeyAuth: [] tags: - name: Assistants description: Build Assistants that can call models and use tools. - name: Audio description: Turn audio into text or text into audio. - name: Chat description: >- Given a list of messages comprising a conversation, the model will return a response. - name: Completions description: >- Given a prompt, the model will return one or more predicted completions, and can also return the probabilities of alternative tokens at each position. - name: Embeddings description: >- Get a vector representation of a given input that can be easily consumed by machine learning models and algorithms. - name: Evals description: Manage and run evals in the OpenAI platform. - name: Fine-tuning description: Manage fine-tuning jobs to tailor a model to your specific training data. - name: Batch description: Create large batches of API requests to run asynchronously. - name: Files description: >- Files are used to upload documents that can be used with features like Assistants and Fine-tuning. - name: Uploads description: Use Uploads to upload large files in multiple parts. - name: Images description: Given a prompt and/or an input image, the model will generate a new image. - name: Models description: List and describe the various models available in the API. - name: Moderations description: >- Given text and/or image inputs, classifies if those inputs are potentially harmful. - name: Audit Logs description: List user actions and configuration changes within this organization. paths: /realtime/sessions: post: tags: - Realtime summary: Create session description: > Create an ephemeral API token for use in client-side applications with the Realtime API. Can be configured with the same session parameters as the `session.update` client event. It responds with a session object, plus a `client_secret` key which contains a usable ephemeral API token that can be used to authenticate browser clients for the Realtime API. operationId: create-realtime-session requestBody: description: Create an ephemeral API key with the given session configuration. required: true content: application/json: schema: $ref: '#/components/schemas/RealtimeSessionCreateRequest' responses: '200': description: Session created successfully. content: application/json: schema: $ref: '#/components/schemas/RealtimeSessionCreateResponse' components: schemas: RealtimeSessionCreateRequest: type: object description: Realtime session object configuration. properties: modalities: description: | The set of modalities the model can respond with. To disable audio, set this to ["text"]. items: type: string default: - text - audio enum: - text - audio model: type: string description: | The Realtime model used for this session. enum: - gpt-4o-realtime-preview - gpt-4o-realtime-preview-2024-10-01 - gpt-4o-realtime-preview-2024-12-17 - gpt-4o-mini-realtime-preview - gpt-4o-mini-realtime-preview-2024-12-17 instructions: type: string description: > The default system instructions (i.e. system message) prepended to model calls. This field allows the client to guide the model on desired responses. The model can be instructed on response content and format, (e.g. "be extremely succinct", "act friendly", "here are examples of good responses") and on audio behavior (e.g. "talk quickly", "inject emotion into your voice", "laugh frequently"). The instructions are not guaranteed to be followed by the model, but they provide guidance to the model on the desired behavior. Note that the server sets default instructions which will be used if this field is not set and are visible in the `session.created` event at the start of the session. voice: $ref: '#/components/schemas/VoiceIdsShared' description: > The voice the model uses to respond. Voice cannot be changed during the session once the model has responded with audio at least once. Current voice options are `alloy`, `ash`, `ballad`, `coral`, `echo`, `fable`, `onyx`, `nova`, `sage`, `shimmer`, and `verse`. input_audio_format: type: string default: pcm16 enum: - pcm16 - g711_ulaw - g711_alaw description: > The format of input audio. Options are `pcm16`, `g711_ulaw`, or `g711_alaw`. For `pcm16`, input audio must be 16-bit PCM at a 24kHz sample rate, single channel (mono), and little-endian byte order. output_audio_format: type: string default: pcm16 enum: - pcm16 - g711_ulaw - g711_alaw description: > The format of output audio. Options are `pcm16`, `g711_ulaw`, or `g711_alaw`. For `pcm16`, output audio is sampled at a rate of 24kHz. input_audio_transcription: type: object description: > Configuration for input audio transcription, defaults to off and can be set to `null` to turn off once on. Input audio transcription is not native to the model, since the model consumes audio directly. Transcription runs asynchronously through [the /audio/transcriptions endpoint](https://platform.openai.com/docs/api-reference/audio/createTranscription) and should be treated as guidance of input audio content rather than precisely what the model heard. The client can optionally set the language and prompt for transcription, these offer additional guidance to the transcription service. properties: model: type: string description: > The model to use for transcription, current options are `gpt-4o-transcribe`, `gpt-4o-mini-transcribe`, and `whisper-1`. language: type: string description: > The language of the input audio. Supplying the input language in [ISO-639-1](https://en.wikipedia.org/wiki/List_of_ISO_639-1_codes) (e.g. `en`) format will improve accuracy and latency. prompt: type: string description: > An optional text to guide the model's style or continue a previous audio segment. For `whisper-1`, the [prompt is a list of keywords](/docs/guides/speech-to-text#prompting). For `gpt-4o-transcribe` models, the prompt is a free text string, for example "expect words related to technology". turn_detection: type: object description: > Configuration for turn detection, ether Server VAD or Semantic VAD. This can be set to `null` to turn off, in which case the client must manually trigger model response. Server VAD means that the model will detect the start and end of speech based on audio volume and respond at the end of user speech. Semantic VAD is more advanced and uses a turn detection model (in conjuction with VAD) to semantically estimate whether the user has finished speaking, then dynamically sets a timeout based on this probability. For example, if user audio trails off with "uhhm", the model will score a low probability of turn end and wait longer for the user to continue speaking. This can be useful for more natural conversations, but may have a higher latency. properties: type: type: string default: server_vad enum: - server_vad - semantic_vad description: | Type of turn detection. eagerness: type: string default: auto enum: - low - medium - high - auto description: > Used only for `semantic_vad` mode. The eagerness of the model to respond. `low` will wait longer for the user to continue speaking, `high` will respond more quickly. `auto` is the default and is equivalent to `medium`. threshold: type: number description: > Used only for `server_vad` mode. Activation threshold for VAD (0.0 to 1.0), this defaults to 0.5. A higher threshold will require louder audio to activate the model, and thus might perform better in noisy environments. prefix_padding_ms: type: integer description: > Used only for `server_vad` mode. Amount of audio to include before the VAD detected speech (in milliseconds). Defaults to 300ms. silence_duration_ms: type: integer description: > Used only for `server_vad` mode. Duration of silence to detect speech stop (in milliseconds). Defaults to 500ms. With shorter values the model will respond more quickly, but may jump in on short pauses from the user. create_response: type: boolean default: true description: > Whether or not to automatically generate a response when a VAD stop event occurs. interrupt_response: type: boolean default: true description: > Whether or not to automatically interrupt any ongoing response with output to the default conversation (i.e. `conversation` of `auto`) when a VAD start event occurs. input_audio_noise_reduction: type: object default: null description: > Configuration for input audio noise reduction. This can be set to `null` to turn off. Noise reduction filters audio added to the input audio buffer before it is sent to VAD and the model. Filtering the audio can improve VAD and turn detection accuracy (reducing false positives) and model performance by improving perception of the input audio. properties: type: type: string enum: - near_field - far_field description: > Type of noise reduction. `near_field` is for close-talking microphones such as headphones, `far_field` is for far-field microphones such as laptop or conference room microphones. tools: type: array description: Tools (functions) available to the model. items: type: object properties: type: type: string enum: - function description: The type of the tool, i.e. `function`. x-stainless-const: true name: type: string description: The name of the function. description: type: string description: > The description of the function, including guidance on when and how to call it, and guidance about what to tell the user when calling (if anything). parameters: type: object description: Parameters of the function in JSON Schema. tool_choice: type: string default: auto description: > How the model chooses tools. Options are `auto`, `none`, `required`, or specify a function. temperature: type: number default: 0.8 description: > Sampling temperature for the model, limited to [0.6, 1.2]. For audio models a temperature of 0.8 is highly recommended for best performance. max_response_output_tokens: oneOf: - type: integer - type: string enum: - inf x-stainless-const: true description: | Maximum number of output tokens for a single assistant response, inclusive of tool calls. Provide an integer between 1 and 4096 to limit output tokens, or `inf` for the maximum available tokens for a given model. Defaults to `inf`. RealtimeSessionCreateResponse: type: object description: > A new Realtime session configuration, with an ephermeral key. Default TTL for keys is one minute. properties: client_secret: type: object description: Ephemeral key returned by the API. properties: value: type: string description: > Ephemeral key usable in client environments to authenticate connections to the Realtime API. Use this in client-side environments rather than a standard API token, which should only be used server-side. expires_at: type: integer description: > Timestamp for when the token expires. Currently, all tokens expire after one minute. required: - value - expires_at modalities: description: | The set of modalities the model can respond with. To disable audio, set this to ["text"]. items: type: string enum: - text - audio instructions: type: string description: > The default system instructions (i.e. system message) prepended to model calls. This field allows the client to guide the model on desired responses. The model can be instructed on response content and format, (e.g. "be extremely succinct", "act friendly", "here are examples of good responses") and on audio behavior (e.g. "talk quickly", "inject emotion into your voice", "laugh frequently"). The instructions are not guaranteed to be followed by the model, but they provide guidance to the model on the desired behavior. Note that the server sets default instructions which will be used if this field is not set and are visible in the `session.created` event at the start of the session. voice: $ref: '#/components/schemas/VoiceIdsShared' description: > The voice the model uses to respond. Voice cannot be changed during the session once the model has responded with audio at least once. Current voice options are `alloy`, `ash`, `ballad`, `coral`, `echo` `sage`, `shimmer` and `verse`. input_audio_format: type: string description: > The format of input audio. Options are `pcm16`, `g711_ulaw`, or `g711_alaw`. output_audio_format: type: string description: > The format of output audio. Options are `pcm16`, `g711_ulaw`, or `g711_alaw`. input_audio_transcription: type: object description: > Configuration for input audio transcription, defaults to off and can be set to `null` to turn off once on. Input audio transcription is not native to the model, since the model consumes audio directly. Transcription runs asynchronously through Whisper and should be treated as rough guidance rather than the representation understood by the model. properties: model: type: string description: > The model to use for transcription, `whisper-1` is the only currently supported model. turn_detection: type: object description: > Configuration for turn detection. Can be set to `null` to turn off. Server VAD means that the model will detect the start and end of speech based on audio volume and respond at the end of user speech. properties: type: type: string description: > Type of turn detection, only `server_vad` is currently supported. threshold: type: number description: > Activation threshold for VAD (0.0 to 1.0), this defaults to 0.5. A higher threshold will require louder audio to activate the model, and thus might perform better in noisy environments. prefix_padding_ms: type: integer description: | Amount of audio to include before the VAD detected speech (in milliseconds). Defaults to 300ms. silence_duration_ms: type: integer description: > Duration of silence to detect speech stop (in milliseconds). Defaults to 500ms. With shorter values the model will respond more quickly, but may jump in on short pauses from the user. tools: type: array description: Tools (functions) available to the model. items: type: object properties: type: type: string enum: - function description: The type of the tool, i.e. `function`. x-stainless-const: true name: type: string description: The name of the function. description: type: string description: > The description of the function, including guidance on when and how to call it, and guidance about what to tell the user when calling (if anything). parameters: type: object description: Parameters of the function in JSON Schema. tool_choice: type: string description: > How the model chooses tools. Options are `auto`, `none`, `required`, or specify a function. temperature: type: number description: > Sampling temperature for the model, limited to [0.6, 1.2]. Defaults to 0.8. max_response_output_tokens: oneOf: - type: integer - type: string enum: - inf x-stainless-const: true description: | Maximum number of output tokens for a single assistant response, inclusive of tool calls. Provide an integer between 1 and 4096 to limit output tokens, or `inf` for the maximum available tokens for a given model. Defaults to `inf`. required: - client_secret x-oaiMeta: name: The session object group: realtime example: | { "id": "sess_001", "object": "realtime.session", "model": "gpt-4o-realtime-preview", "modalities": ["audio", "text"], "instructions": "You are a friendly assistant.", "voice": "alloy", "input_audio_format": "pcm16", "output_audio_format": "pcm16", "input_audio_transcription": { "model": "whisper-1" }, "turn_detection": null, "tools": [], "tool_choice": "none", "temperature": 0.7, "max_response_output_tokens": 200, "client_secret": { "value": "ek_abc123", "expires_at": 1234567890 } } VoiceIdsShared: example: ash anyOf: - type: string - type: string enum: - alloy - ash - ballad - coral - echo - fable - onyx - nova - sage - shimmer - verse securitySchemes: ApiKeyAuth: type: http scheme: bearer ````