polymerdao/polymer-pay-x402engine-audio

x402engine Audio

x402engine provides pay-per-call text-to-speech and audio transcription endpoints. Convert text to speech using OpenAI or ElevenLabs voices, or transcribe audio files to text with speaker diarization. No API key needed — payment is handled automatically by the Polymer Pay proxy.

Authentication

All requests route through the Polymer Pay proxy. Include your Polymer Pay API key in every request:

{
  "headers": {
    "Content-Type": "application/json",
    "x-polymer-pay-api-key": "{{POLYMER_PAY_API_KEY}}"
  }
}

Base URL: https://pay.polymerlabs.org/proxy/https/x402engine.app

To get an Polymer Pay API key, sign up at https://my.pay.polymerlabs.org/dashboard/api-keys.

Common Operations

Text-to-Speech (OpenAI)

Generate speech audio from text using OpenAI's TTS models.

Pricing: $0.01

{
  "method": "POST",
  "url": "https://pay.polymerlabs.org/proxy/https/x402engine.app/api/tts/openai",
  "headers": {
    "Content-Type": "application/json",
    "x-polymer-pay-api-key": "{{POLYMER_PAY_API_KEY}}"
  },
  "body": {
    "text": "Hello, this is a test of text-to-speech generation.",
    "voice": "alloy"
  }
}

Available voices: alloy, echo, fable, onyx, nova, shimmer

Response: Returns audio data (MP3 or other format). Save to a file with -o output.mp3.

Text-to-Speech (ElevenLabs)

Generate ultra-realistic speech using ElevenLabs voices.

Pricing: $0.02

{
  "method": "POST",
  "url": "https://pay.polymerlabs.org/proxy/https/x402engine.app/api/tts/elevenlabs",
  "headers": {
    "Content-Type": "application/json",
    "x-polymer-pay-api-key": "{{POLYMER_PAY_API_KEY}}"
  },
  "body": {
    "text": "Welcome to the future of AI-generated speech.",
    "voice": "rachel"
  }
}

Response: Returns ultra-realistic audio data. ElevenLabs voices are more natural and expressive but cost 2x more.

Audio Transcription (Deepgram Nova-3)

Transcribe audio files to text with speaker diarization.

Pricing: $0.10

{
  "method": "POST",
  "url": "https://pay.polymerlabs.org/proxy/https/x402engine.app/api/transcribe",
  "headers": {
    "Content-Type": "multipart/form-data",
    "x-polymer-pay-api-key": "{{POLYMER_PAY_API_KEY}}"
  },
  "body": {
    "file": "@recording.mp3"
  }
}

Response: JSON with transcribed text, speaker diarization labels, and timestamps.

When to Use

• Text-to-speech — User wants to convert text to speech or generate audio from text
• Audio transcription — User wants to transcribe an audio file to text
• TTS specifically — User asks for TTS, text-to-speech, or voice generation
• Transcription — User asks for speech-to-text, transcription, or audio-to-text
• ElevenLabs/OpenAI — User mentions ElevenLabs, OpenAI TTS, or Deepgram

Best Practices

• OpenAI TTS — $0.01, reliable, 6 voices, HD quality, good for most use cases
• ElevenLabs TTS — $0.02, ultra-realistic, multilingual, best voice quality
• Transcription — $0.10 includes speaker diarization with labels and timestamps
• Save TTS output — TTS endpoints return audio binary; always use -o filename.mp3 to save output
• Multipart for transcription — For transcription, send the audio file as multipart form data
• For errors — See @skills/polymer-pay-api-errors/SKILL.md for complete error code reference and troubleshooting