API ReferenceAssistants

Create an assistant

Authentication

AuthorizationBearer

Bearer authentication of the form Bearer <token>, where token is your auth token.

Request

Body
promptstringRequired

The prompt to use for the call. This will be given to the LLM (gpt-4.1)

namestringRequired
first_sentencestringOptional
The first sentence to use for the call. This will be given to the LLM
first_sentence_modeenumOptional

How the first sentence should be handled. “generated” means the LLM will generate a response based on the first_sentence instruction. “static” means the first_sentence will be spoken exactly as provided. “none” means the agent will not speak first and will wait for the user.

Allowed values:
end_of_call_sentencestringOptional
Optional message to say when the agent decides to end the call.
voiceobjectOptional

The voice to use for the call. You can get the list of voices using the /voices endpoint

llm_modelobjectOptional
webhook_urlstringOptional
The webhook URL to call when the call is completed.
max_call_duration_secsdoubleOptional
The maximum duration of the call in seconds. This is the maximum time the call will be allowed to run.
structured_output_configlist of objectsOptional

The structured output config to use for the call. This is used to extract the data from the call (like email, name, company name, etc.).

call_retry_configobjectOptional
Configuration for call retry behavior including time windows, delays, and max iterations. If not provided, defaults will be used.
background_soundenum or nullOptional
The background sound to play during the call. Useful to give the impression that your AI agent is in an office, in the street, or anywhere else you want.
Allowed values:
transfer_phone_numberstring or nullOptional

Phone number to transfer calls to when users request to speak to a human agent in E.164 format (e.g. +1234567890).

ivr_navigation_enabledbooleanOptional
Enable IVR navigation tools. When enabled, the assistant can send DTMF tones and skip turns to navigate phone menus.
voicemail_messagestring or nullOptional

If set, when voicemail is detected the agent will speak this message then hang up; if null, hang up immediately.

first_sentence_delay_msintegerOptional0-9007199254740991

Delay in milliseconds before speaking the first sentence. Default: 400.

faq_itemslist of objectsOptional
FAQ items to associate with this assistant. When provided, replaces all existing FAQ items.
calendlyobjectOptional

Response

200
assistantobject

Errors