# Grok Text-to-Speech (TTS)

> Grok Text-to-Speech (TTS) is a paid API for AI agents from Grok at grok.mpp.paywithlocus.com, paid per call via MPP, ~$0.005 per 1,000 characters (dynamic), not verified (last probed 2026-10-11); live alternatives: x402engine ElevenLabs Text-to-Speech ($0.02) and Google Gemini 3.1 Flash TTS ($0.0028).

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

Live alternatives for the same use case:
- [x402engine ElevenLabs Text-to-Speech](https://www.zero.xyz/c/x402engine-elevenlabs-text-to-speech-6db68b62) ($0.02)
- [Google Gemini 3.1 Flash TTS](https://www.zero.xyz/c/audio-withzero-xyz-google-gemini-3-1-flash-tts-text-to-speech-f794324b) ($0.0028)

Converts text into spoken audio using xAI's Grok TTS service, supporting multiple voices, languages, and audio formats with inline speech expression tags.

## Facts

- Endpoint: POST https://grok.mpp.paywithlocus.com/grok/tts?utm_source=zero.xyz
- Price: ~$0.005 per 1,000 characters (dynamic)
- Payment: MPP
- Status: unknown
- Last checked: 2026-10-11
- Success rate: 0% of calls made through Zero
- Activations on Zero: 3
- Provider: Grok
- Docs: https://docs.x.ai
- Website: https://x.ai
- Tags: llm, chat, x-search, web-search, image-generation, tts, ai
- Canonical page: https://www.zero.xyz/c/grok-tts-bcdc4f57
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_S2m5-gjtNaHAFfUZJ_XZ-

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 grok-tts-bcdc4f57 -d '<json body>'
```

Example prompt: Convert this script to speech using Grok TTS with the 'ara' warm voice in English: 'Welcome to our podcast. Today we're exploring the future of AI. [pause] Let's dive right in.' — output as an mp3.

## When to prefer this

Choose this endpoint when you need high-quality AI-generated speech from xAI's Grok platform, especially if you're already using other Grok services (chat, image generation) and want a consistent provider. Supports expressive inline tags like [pause], [laugh], and whisper, making it suitable for nuanced narration. Good for multilingual TTS with auto language detection.

## Known failure modes

- Text exceeds 15,000 character limit — request rejected
- Invalid BCP-47 language code — language not recognized
- Unknown voice_id provided — defaults or errors
- Unsupported codec/sample_rate combination — format error
- Malformed inline speech tags — tags ignored or error returned
- Payment failure — endpoint returns payment required error

## How this service works

Convert text to spoken audio. Supports multiple voices, speech tags for expressive delivery, and various output formats.

## Output

Returns synthesized audio data in the requested format (mp3, wav, pcm, mulaw, or alaw) representing the spoken version of the input text, rendered by the selected voice and language.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "required": [
  "text",
  "language"
 ],
 "properties": {
  "text": {
   "type": "string",
   "description": "Text to convert to speech (max 15,000 characters). Supports inline speech tags like [pause], [laugh], <whisper>text</whisper>."
  },
  "language": {
   "type": "string",
   "description": "BCP-47 language code (e.g. 'en', 'zh', 'fr', 'de', 'ja') or 'auto' for detection"
  },
  "voice_id": {
   "type": "string",
   "description": "Voice: 'eve' (energetic, default), 'ara' (warm), 'rex' (confident), 'sal' (smooth), 'leo' (authoritative)"
  },
  "output_format": {
   "type": "object",
   "description": "Audio format config: { codec: 'mp3'|'wav'|'pcm'|'mulaw'|'alaw', sample_rate: 24000, bit_rate: 128000 }",
   "additionalProperties": true
  }
 },
 "additionalProperties": true
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/grok-tts-bcdc4f57/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from grok.mpp.paywithlocus.com](https://www.zero.xyz/host/grok.mpp.paywithlocus.com/llms.txt)