# Onchain Router Speech-to-Text Transcription

> Onchain Router Speech-to-Text Transcription is a paid API for AI agents from onchainrouter.dev, paid per call via x402, $0.002/call, status unknown (last checked 2026-09-15).

Transcribes audio to text using the ElevenLabs Scribe v2 model, accepting Base64-encoded audio and returning the transcribed text with usage metadata

## Facts

- Endpoint: POST https://onchainrouter.dev/v1/audio/transcriptions
- Price: $0.002/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-15
- Activations on Zero: 5
- Tags: x402
- Canonical page: https://www.zero.xyz/c/onchain-router-speech-to-text-transcription-e71f3400
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_bsURMepz8PpRbTmWKmp8Q

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 onchain-router-speech-to-text-transcription-e71f3400 -d '<json body>'
```

Example prompt: Please transcribe this audio recording for me — encode the file as Base64 and run it through the ElevenLabs Scribe v2 model, returning the result as verbose JSON with timestamps.

## When to prefer this

Choose this endpoint when you need affordable, high-quality speech-to-text transcription powered by ElevenLabs Scribe v2 and want to pay per-call via USDC on-chain with no subscription. Ideal for agents operating autonomously that need programmatic audio transcription without managing API keys for ElevenLabs directly. The 0% service fee launch promotion makes it cost-competitive for high-volume transcription workloads.

## Known failure modes

- Audio Base64 string too short (<4 chars) or too long (>34MB encoded) returns a validation error
- Invalid or unsupported audio format may result in poor or empty transcription
- Malformed Base64 (with data-URL prefix or whitespace) will likely cause a decode error
- Network or payment failure (x402 protocol) prevents the request from completing
- Model not found or unavailable returns an error if enum value is incorrect

## How this service works

Give agents provider-neutral access to text, image, and speech models with USDC payments on Base, local spending controls, ambiguity-safe recovery, and verified receipts. Stable public npm clients and MIT agent integrations are available now.

## Output

Returns a JSON object containing a transcription ID, the full transcribed text string, the model used (elevenlabs/scribe-v2), and usage metadata including the duration of the input audio in milliseconds. Optionally returns verbose JSON with additional detail.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "model": {
   "enum": [
    "elevenlabs/scribe-v2"
   ],
   "type": "string"
  },
  "file_format": {
   "enum": [
    "other"
   ],
   "type": "string",
   "default": "other"
  },
  "audio_base64": {
   "type": "string",
   "format": "byte",
   "maxLength": 34952536,
   "minLength": 4,
   "description": "Canonical RFC 4648 Base64 audio without a data-URL prefix or whitespace."
  },
  "response_format": {
   "enum": [
    "json",
    "verbose_json"
   ],
   "type": "string"
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "id": "trns_example",
  "text": "Transcribed speech.",
  "model": "elevenlabs/scribe-v2",
  "usage": {
   "input_audio_ms": 3100
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/onchain-router-speech-to-text-transcription-e71f3400/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from onchainrouter.dev](https://www.zero.xyz/host/onchainrouter.dev/llms.txt)