Text to speech

Turn text into spoken audio. The endpoint is compatible with OpenAI Audio Speech, so the official OpenAI SDKs work with the base URL https://kenari.id/v1. Only text-to-speech models are served here. Sending any other model returns 400.

POST /v1/audio/speech

Request

The body is JSON.

Field	Type	Required	Description
`model`	string	yes	Text-to-speech model id, for example `gemini-3-1-flash-tts`.
`input`	string	yes	The text to speak. See Text length limit.
`voice`	string	no	Voice name. Names differ per model. Leave it out for the model’s default voice. See Choosing a voice.
`response_format`	string	no	`mp3`, `wav`, `pcm`, `opus`, `aac` or `flac`. Not every model produces all of them. Leave it out for the model’s default. See Choosing a format.
`speed`	number	no	Speaking speed. Applied only by models that support it.
`language`	string	no	Language code, for example `id` or `en`. Detected automatically when left out.

Response

The response body is the raw audio, not JSON. The Content-Type follows the format you asked for.

Format	`Content-Type`
`mp3`	`audio/mpeg`
`wav`	`audio/wav`
`pcm`	`audio/pcm`
`opus`	`audio/ogg`
`aac`	`audio/aac`
`flac`	`audio/flac`

Choosing a voice

Every model has its own voice names, and they are not interchangeable. kenari passes voice to the model as you send it. The voices a model offers are listed in the voices field of that model in GET /v1/models:

curl -s https://kenari.id/v1/models \
  | jq '.data[] | select(.endpoints | index("audio_speech")) | {id, voices}'

The first entry in voices is the default, used when you leave voice out.
Names are matched without regard to case.
A model without a voices field has no recorded list. kenari does not check voice for it and passes the value to the model.
A voice outside the list returns 400 with the allowed names, and nothing is charged.

There is no separate field for speaking style. Put the direction in front of the text, for example Read this like a newscaster: ....

Choosing a format

The formats a model can produce are in the formats field of that model in GET /v1/models:

curl -s https://kenari.id/v1/models \
  | jq '.data[] | select(.endpoints | index("audio_speech")) | {id, formats}'

The first entry in formats is the default, used when you leave response_format out.
Names are matched without regard to case.
A format outside the list returns 400 with the allowed names, and nothing is charged. kenari never swaps in a different format, because the Content-Type would then describe the wrong file.
A model without a formats field accepts mp3, wav and pcm. Any other value gives you mp3, and the Content-Type is audio/mpeg. So opus, aac and flac work only on models that list them in formats.

Text length limit

Synthesis is not streamed, and each provider enforces its own time limit, so text that is too long cannot finish. When a model records a limit, it appears as max_input_chars in GET /v1/models, and longer text returns 400 before anything is charged. Without that field kenari does not cap the length, but a very long request can still fail on the provider’s time limit. Split long text into several requests.

Examples

curl

curl https://kenari.id/v1/audio/speech \
  -H "Authorization: Bearer $KENARI_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "gemini-3-1-flash-tts",
    "input": "Hello, welcome to kenari.",
    "voice": "Kore",
    "response_format": "mp3"
  }' \
  --output speech.mp3

Python

import os

from openai import OpenAI

client = OpenAI(
    base_url="https://kenari.id/v1",
    api_key=os.environ["KENARI_API_KEY"],
)

response = client.audio.speech.create(
    model="gemini-3-1-flash-tts",
    input="Hello, welcome to kenari.",
    voice="Kore",
    response_format="mp3",
)
response.write_to_file("speech.mp3")

JavaScript

import fs from "node:fs";
import OpenAI from "openai";

const client = new OpenAI({
  baseURL: "https://kenari.id/v1",
  apiKey: process.env.KENARI_API_KEY,
});

const response = await client.audio.speech.create({
  model: "gemini-3-1-flash-tts",
  input: "Hello, welcome to kenari.",
  voice: "Kore",
  response_format: "mp3",
});
fs.writeFileSync("speech.mp3", Buffer.from(await response.arrayBuffer()));

Billing

Text to speech is billed per 1,000 characters of input, rounded up. The amount is held when the request is accepted and released if no audio is delivered. See How billing works and the model’s price in Models and pricing.

Errors

Status	Code	When
400	`bad_request`	The model is not a text-to-speech model, `input` is empty, `voice` or `response_format` is not available for the model, or `input` is longer than `max_input_chars`.
402	`insufficient_balance`	The balance does not cover the request.
503	`all_providers_failed`, `upstream_error`	No provider could produce the audio. Nothing is charged. Retry.

See Errors for every other code.