# agent402.tools TTS-HD (High-Fidelity Text-to-Speech)

> agent402.tools TTS-HD (High-Fidelity Text-to-Speech) is a paid API for AI agents from agent402.tools, paid per call via x402, $0.1/call, status unknown (last checked 2026-09-13).

Converts text to high-fidelity speech audio using OpenAI TTS-1-HD, returning base64-encoded audio in your chosen format and voice, paid per call via x402.

## Facts

- Endpoint: POST https://agent402.tools/api/tts-hd
- Price: $0.1/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-13
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/agent402-tools-tts-hd-high-fidelity-text-to-speech-576e2ea0
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_Pd18grxFjNlIWZLWBki01

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 agent402-tools-tts-hd-high-fidelity-text-to-speech-576e2ea0 -d '<json body>'
```

Example prompt: Read this aloud in a high-fidelity voice: 'Welcome to our product demo — today we will walk you through the key features.' Use the nova voice and give me the audio as an mp3.

## When to prefer this

Choose this endpoint over the standard TTS endpoint (/api/tts) when audio quality is the priority — TTS-1-HD uses OpenAI's higher-fidelity model and produces noticeably better audio, especially for content like narration, podcasts, or professional announcements. Prefer this when output quality matters more than minimal cost difference. No API key required; just pay per call.

## Known failure modes

- Text exceeds 2000 character limit — request rejected
- Invalid voice name provided — returns error
- Invalid audio format specified — returns error
- Payment via x402 not completed or insufficient — request blocked
- Empty text input — returns error

## How this service works

Convert text to speech using OpenAI TTS-1-HD (higher fidelity). Returns base64-encoded audio. Same interface as /api/tts but with better audio quality. No API key needed; pay per call via x402. Text capped at 2000 chars.

## Output

A base64-encoded audio file in the requested format (mp3, opus, aac, flac, wav, or pcm) containing synthesized speech of the input text rendered with OpenAI's TTS-1-HD high-fidelity model.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "text": {
   "type": "string",
   "description": "Text to convert to speech (max 2000 chars)"
  },
  "voice": {
   "type": "string",
   "description": "Voice: alloy, ash, ballad, coral, echo, fable, nova, onyx, sage, shimmer (default: alloy)"
  },
  "format": {
   "type": "string",
   "description": "Audio format: mp3, opus, aac, flac, wav, pcm (default: mp3)"
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "audio": "<base64-encoded audio>",
  "chars": 20,
  "model": "tts-1-hd",
  "voice": "alloy",
  "format": "mp3",
  "provider": "openai"
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/agent402-tools-tts-hd-high-fidelity-text-to-speech-576e2ea0/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from agent402.tools](https://www.zero.xyz/host/agent402.tools/llms.txt)