# Neurodynamic TTS – Kokoro English Speech Synthesis

> Neurodynamic TTS – Kokoro English Speech Synthesis is a paid API for AI agents from api.neurodynamic.tech, paid per call via x402, $0.005/call, status unknown (last checked 2026-09-14).

Converts up to 1,000 characters of English text into an MP3 audio file using one of seven Kokoro voices, settled via 0.005 USDC on Base.

## Facts

- Endpoint: POST https://api.neurodynamic.tech/v1/audio/speech
- Price: $0.005/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-14
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/neurodynamic-tts-kokoro-english-speech-synthesis-0d145a34
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_FwQQQ4fBMNY6gFStDnctE

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 neurodynamic-tts-kokoro-english-speech-synthesis-0d145a34 -d '<json body>'
```

Example prompt: Read this product description aloud using the af_heart voice and give me an MP3: 'Introducing our new espresso blend — rich, bold, and perfect for your morning routine.'

## When to prefer this

Choose this endpoint when you need quick, low-cost English TTS with no account setup, no reference audio upload, and no human approval step. It is ideal for agents that need to generate short narrations on demand and can settle micropayments in USDC on Base. Prefer it over larger TTS platforms when cost per call matters and the content fits within 1,000 characters. If you need voice cloning or WAV output, consider the sibling clone-speech endpoint on the same host.

## Known failure modes

- Text exceeds 1,000 characters — request rejected before audio is generated
- Payment proof invalid or expired — 401/402 response, no charge incurred
- Unsupported voice or model value — validation error returned
- Network timeout before audio delivery — retry with identical body and proof within one hour at no extra charge
- Base blockchain congestion causing payment settlement delay

## How this service works

Introductory pricing. Catalogue narration: 0.005 USDC on Base, up to 1,000 characters, MP3. Seven English voices. No account, reference upload or human approval. Read https://api.neurodynamic.tech/narration. Authorisation verified before work; settlement after successful audio. Retry identical body and proof for one hour without a second charge. Quoted tier price: 0.005 USDC.

## Output

A raw MP3 binary (audio/mpeg) containing the synthesized speech of the submitted text, ready to save or stream directly. No metadata envelope — just the audio bytes.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "input": {
   "type": "string",
   "maxLength": 1000
  },
  "model": {
   "enum": [
    "kokoro"
   ]
  },
  "speed": {
   "enum": [
    1
   ]
  },
  "voice": {
   "enum": [
    "af_heart",
    "af_bella",
    "bf_emma",
    "bf_alice",
    "bm_george",
    "am_michael",
    "am_fenrir"
   ],
   "type": "string"
  },
  "stream": {
   "enum": [
    false
   ]
  },
  "response_format": {
   "enum": [
    "mp3"
   ]
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "binary",
 "format": "audio/mpeg",
 "example": "<MP3 bytes>"
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/neurodynamic-tts-kokoro-english-speech-synthesis-0d145a34/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from api.neurodynamic.tech](https://www.zero.xyz/host/api.neurodynamic.tech/llms.txt)