OpenAI text to speech for AI agents: voice with the key you have

What is OpenAI text to speech?

OpenAI's Audio API has a speech endpoint that reads text aloud in one of 13 built-in voices, such as Alloy, Coral, Marin and Cedar, and a transcription endpoint that turns a recording into text. Both are reached with an ordinary OpenAI API key.

OpenAI has announced that its current speech models, including gpt-4o-mini-tts, shut down on January 6, 2027. Its replacement, gpt-realtime-2.1-mini, works through the Realtime API instead of the speech endpoint. The gpt-4o-mini-transcribe transcription model follows on February 26, 2027.

What you can do with OpenAI in SFCrew

OpenAI both speaks and transcribes, so it covers every voice feature in SFCrew. The voice and calls guide shows where each control lives.

• Talk instead of typing. Hold the mic in the composer, speak, and let go to send. When SFCrew transcribes on the server, as it does in a phone browser or the desktop app, it uses gpt-4o-mini-transcribe.
• Hear replies. Choose Speak this reply on any message, or turn on Read replies aloud in a bot's settings. Replies are spoken with gpt-4o-mini-tts.
• Call a bot. Choose Call at the top of a chat to talk in real time. You can cut in while the bot is speaking, and the transcript stays in the chat.
• Get called. Ask "call me when the drafts are ready" and the bot rings you. A bot may also call if you've missed the same reminder several times.
• Give each bot its own voice. Pick from OpenAI's 13 voices per bot, so different bots are easy to tell apart.
• Send voice notes from chat apps. A voice note sent to a bot through Telegram, for example, is transcribed before the bot reads it. See messaging apps.

When to choose OpenAI

Choose OpenAI when you already have an OpenAI account and want voice working in a few minutes, with clear voices and solid transcription from one key. Because its speech models are scheduled to shut down, treat it as a convenient start rather than a long-term pick, until SFCrew moves to OpenAI's newer models.

ElevenLabs also speaks and transcribes, with more natural voices and support for your own cloned ones. Cartesia is built for fast, interruptible calls but only speaks. Fish Audio offers cloning and expressive speech. If you like OpenAI's API shape but want audio on your own hardware, a self-hosted server such as Kokoro or Whisper speaks the same protocol. macOS voices need no key when your server runs on a Mac. The comparison puts them side by side.

Limits

• SFCrew speaks with gpt-4o-mini-tts, which OpenAI shuts down on January 6, 2027, and transcribes with gpt-4o-mini-transcribe, which follows on February 26, 2027. Until SFCrew moves to newer models, OpenAI voice stops working on those dates.
• The models are fixed. You can't choose tts-1, a newer model or a different transcription model from SFCrew.
• SFCrew offers OpenAI's 13 built-in voices. It doesn't send tone instructions, and custom voices made in your OpenAI account aren't supported.
• Each sentence is generated as a finished clip and played in order, rather than streamed, so there is a short pause before the bot starts talking.
• OpenAI's usage policies ask you to tell listeners the voice is AI-generated. Keep that in mind if a bot's voice reaches people outside your team.
• Calls and hold-to-talk are a server setting. On a self-hosted server they stay off until the admin turns them on.

How to set it up

Anyone can do this in their own settings, on SFCrew Cloud or a self-hosted server. The key belongs to your account, and it is stored separately from any OpenAI key you use for models, so paste it here even if you already added it elsewhere.

1. Create an API key in the OpenAI platform for a project with audio access.
2. In SFCrew, open Settings → Voice, choose OpenAI as the Provider, paste the API key and choose Connect.
3. Pick a Voice, such as Marin or Cedar, and use Hear a sample to check it.
4. Optionally, open a bot's settings, expand Advanced, turn on Read replies aloud and give it its own Voice.
5. If you run your own server and want calls and hold-to-talk, set PHONE_CALLS_ENABLED=true on the API and worker.