Audio Transcription MCP

Audio transcription with OpenAI Whisper and x402 micropayments on Base.

Features

• 🎤 AI Speech-to-Text - Transcribe audio files using OpenAI Whisper

• 💳 x402 Payments - Pay $0.010 USDC per transcription via Base mainnet

• 🌍 Multi-Language - Support for 50+ languages with auto-detection

• 📁 Multiple Formats - MP3, WAV, M4A, MP4, WebM, OGG, FLAC

• 🔗 URL Support - Transcribe audio from URLs

• 🔒 Payment Verification - Secure payment verification via Coinbase CDP Facilitator

Related MCP server: transcribe-mcp

Live Demo

🌐 Service URL: https://audio-transcription-mcp.vercel.app

API Endpoints

POST /api/transcribe

Transcribe audio file (multipart/form-data upload)

Request:

curl -X POST https://audio-transcription-mcp.vercel.app/api/transcribe \
  -H "PAYMENT-SIGNATURE: your_payment_signature" \
  -F "file=@audio.mp3" \
  -F "language=en"

Parameters:

• file (required) - Audio file (max 25MB)

• language (optional) - Language code (e.g., en, es, fr, de, ja, zh)

Response:

{
  "success": true,
  "text": "This is the transcribed text from the audio file.",
  "language": "en",
  "fileName": "audio.mp3",
  "fileSize": 1048576,
  "transcribedAt": "2026-09-06T10:45:00.000Z",
  "payment": {
    "verified": true,
    "amount": "0.010",
    "currency": "USDC"
  }
}

POST /api/transcribe-url

Transcribe audio from URL

Request:

{
  "url": "https://example.com/audio.mp3",
  "language": "en"
}

Parameters:

• url (required) - URL of the audio file

• language (optional) - Language code (e.g., en, es, fr, de, ja, zh)

Response:

{
  "success": true,
  "text": "This is the transcribed text from the audio file.",
  "language": "en",
  "url": "https://example.com/audio.mp3",
  "fileSize": 1048576,
  "transcribedAt": "2026-09-06T10:45:00.000Z",
  "payment": {
    "verified": true,
    "amount": "0.010",
    "currency": "USDC"
  }
}

GET /.well-known/x402

x402 Bazaar discovery endpoint (free)

GET /mcp/tools

MCP tool metadata (free)

GET /health

Health check endpoint (free)

Supported Languages

English (en), Spanish (es), French (fr), German (de), Italian (it), Portuguese (pt), Dutch (nl), Russian (ru), Chinese (zh), Japanese (ja), Korean (ko), Arabic (ar), Hindi (hi), and 40+ more.

Supported Audio Formats

• MP3 - MPEG audio

• WAV - Waveform audio

• M4A - MPEG-4 audio

• MP4 - MPEG-4 container with audio

• WebM - WebM audio

• OGG - Ogg Vorbis audio

• FLAC - Free Lossless Audio Codec

File size limit: 25MB (Whisper API limit)

Payment Details

• Network: Base Mainnet (eip155:8453)

• Currency: USDC

• Price: $0.010 per transcription

• Protocol: x402 v2 "exact" scheme

• Payment Address: 0xf081ee84c0d85278a6242bc265f0b312021ebeb1

Setup

Prerequisites

• Node.js 18+

• OpenAI API key

• Vercel account (for deployment)

Installation

npm install

Environment Variables

Create a .env file:

OPENAI_API_KEY=your_openai_api_key_here
X402_FACILITATOR_URL=https://api.cdp.coinbase.com/platform/v2/x402
PORT=3000

Local Development

npm start

Server runs on http://localhost:3000

Deployment

Deploy to Vercel

# Install Vercel CLI
npm i -g vercel

# Deploy
vercel

# Set environment variable
vercel env add OPENAI_API_KEY

Add your OpenAI API key when prompted.

How x402 Payment Works

1. Agent calls /api/transcribe without payment

2. Server returns 402 with payment details in PAYMENT-REQUIRED header

3. Agent pays $0.010 USDC on Base via CDP Facilitator

4. Agent retries with PAYMENT-SIGNATURE header

5. Server verifies payment and transcribes audio

Tech Stack

• Express.js - Web server

• @x402/core - Payment verification

• OpenAI Whisper - Audio transcription

• Multer - File upload handling

• Base Mainnet - Low-fee L2 blockchain

• Vercel - Serverless deployment

License

MIT

Support

For issues or questions, open an issue on GitHub.