# OpenAI Text-to-Speech (TTS)

> OpenAI Text-to-Speech (TTS) is a paid API for AI agents from OpenAI at openai.mpp.tempo.xyz, paid per call via MPP, $0.02/call, live (last probed 2026-10-11, last successful call 2026-09-28).

Agents call it through Zero, which pays per call: no API key and no wallet of your own. New accounts start with $5.

Converts input text into spoken audio using OpenAI's TTS models and voices, returning an audio file in the specified format

## Facts

- Endpoint: POST https://openai.mpp.tempo.xyz/v1/audio/speech?utm_source=zero.xyz
- Price: $0.02/call
- Payment: MPP
- Status: healthy
- Last checked: 2026-10-11
- Last successful call: 2026-09-28
- Success rate: 85% of calls made through Zero
- Rating: 4.5 / 5 from 10 reviews
- Activations on Zero: 321
- Provider: OpenAI
- Docs: https://platform.openai.com/docs
- Website: https://openai.com
- Tags: llm, gpt-4o, dall-e, whisper, tts, embeddings, chat, ai, media
- Canonical page: https://www.zero.xyz/c/openai-speech-20f236c8
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_fR9MHn_4lGPPEbDO1TffA

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability openai-speech-20f236c8 -d '<json body>'
```

Example prompt: Can you convert this text to speech using the alloy voice and give me an MP3: 'Welcome to our platform. We're glad you're here.'

## When to prefer this

Use this endpoint when you need high-quality AI-generated speech from OpenAI's TTS models with multiple voice options and audio format choices. Prefer over alternatives when already using OpenAI's ecosystem, when you need consistent voice quality, or when you require specific voices like alloy, echo, fable, onyx, nova, or shimmer. This is the canonical OpenAI TTS endpoint accessible via the mpp/x402 payment protocol at a flat $0.02 USDC per call.

## Known failure modes

- Input text too long (exceeds model token limit) — returns 400 error
- Invalid voice name specified — returns 400 with validation error
- Invalid model specified — returns 400
- Invalid response_format value — returns 400
- Authentication failure (invalid API key) — returns 401
- Rate limit exceeded — returns 429
- Service unavailable — returns 500

## How this service works

Text-to-speech

## Output

A binary audio file (default MP3, or other specified format) containing the synthesized spoken audio of the input text. The response is non-JSON binary content with content-type audio/mpeg (or equivalent for other formats).

## Example request

```json
{
 "input": "Hello, this is a test of the text to speech service.",
 "model": "tts-1",
 "voice": "alloy",
 "response_format": "mp3"
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/openai-speech-20f236c8/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from openai.mpp.tempo.xyz](https://www.zero.xyz/host/openai.mpp.tempo.xyz/llms.txt)