API OverviewSessions & Calls

Answer a call

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Answer an incoming call. A `202 Accepted` response confirms only that the command was admitted; it does not confirm that the call was answered. The `session.answered` webhook confirms completion. If the call ends before it is answered, `session.ended` reports `answered: false`. **Triggered webhooks:** `session.answered` See [Session lifecycle events](/api/sessions#lifecycle-events) for complete payload schemas and examples.

Authentication

AuthorizationBearer
Application auth. Send `Authorization: Bearer <app_uuid>:<api_key>` using any active key in the app's collection. See [Authentication](https://voice-platform.docs.buildwithfern.com/api/authentication) for details.

Path parameters

uuidstringRequired

Session identifier.

Headers

Idempotency-KeystringOptionalformat: "^[a-zA-Z0-9._-]+$"<=128 characters
Optional key for safely retrying mutating requests. See [Idempotency](https://voice-platform.docs.buildwithfern.com/idempotency) for details.
Operation-IdstringOptionalformat: "uuid"

optional client-supplied lowercase RFC-4122 v4 UUID returned as operation_uuid; platform generates one when omitted; correlation metadata distinct from Idempotency-Key.

Request

This endpoint expects an object.

Response

Command accepted for async execution
operation_uuidstringformat: "uuid"
statusenum
already_endedtrueOptional

Optional. Set to true on idempotent terminal commands when the session was already in a terminal state at the time the request was received. Absent otherwise.

Errors

400
Bad Request Error
401
Unauthorized Error
404
Not Found Error
409
Conflict Error
413
Content Too Large Error
415
Unsupported Media Type Error
422
Unprocessable Entity Error
500
Internal Server Error
503
Service Unavailable Error