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Best pay-per-call text to speech APIs for AI agents (September 2026)

Ranked by evidence from Zero's own probes and real agent calls · Updated Sep 29, 2026 · 66 agents searched Zero for this in the last 90 days

Zero indexes 45 pay-per-call services for text to speech. Of the 10 ranked here, 9 answered a live probe in the last 7 days. Quoted prices run from $0.002 to $0.21 per call, median $0.03, paid per call over x402 or MPP with no API key. The three with real agent usage in the last 30 days are agent402.tools Text-to-Speech, Google Gemini 3.1 Flash TTS, Arch Tools. The cheapest live option is Onchain Router Speech-to-Text Transcription at $0.002.

  1. agent402.toolsagent402.tools Text-to-Speech (OpenAI TTS-1)4.8(2)382x402

    Converts input text (up to 2000 chars) to base64-encoded audio using OpenAI TTS-1, with 10 voice options and multiple output formats, paid per-call via x402.

    $0.05/message

    Live · checked Oct 2, 2026340 calls · 30 days

  2. audio.withzero.xyzGoogle Gemini 3.1 Flash TTS – Text-to-Speech4.9(3)3.3kmpp

    Converts text (up to 4000 characters) to natural-sounding speech using Google Gemini 3.1 Flash TTS and returns a hosted WAV audio URL.

    $0.00356/message

    Live · checked Oct 2, 2026141 calls · 30 days

  3. archtools.devArch Tools – Audio Transcription21x402

    Transcribes an audio file from a public URL into text, with optional language hint and context prompt for improved accuracy

    $0.03/message

    Live · checked Oct 2, 202619 calls · 30 days

  4. agents.dexl.ioDexL Agents Audio Transcription12x402

    Converts base64-encoded audio files (WAV, MP3, FLAC, OGG) into plain text transcripts, paid per call via x402.

    $0.002508/message

    Live · checked Oct 2, 202612 calls · 30 days

  5. openai.mpp.tempo.xyzOpenAI Text-to-Speech (TTS)llm4.5(10)321mpp

    Converts input text into spoken audio using OpenAI's TTS models and voices, returning an audio file in the specified format

    $0.02/message

    Live · checked Oct 2, 202610 calls · 30 days

  6. onchainrouter.devOnchain Router Speech-to-Text Transcription5x402

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

    $0.002/message

    Live · checked Oct 2, 20265 calls · 30 days

  7. agents.withzero.xyzWithZero Whisper Large V3 Audio Transcription3.7(3)13x402

    Transcribes base64-encoded audio (WAV or MP3) into text using OpenAI's Whisper Large V3 model via a pay-per-use proxy

    $0.12/message

    Live · checked Oct 2, 20264 calls · 30 days

  8. gambit.barrioenergy.comGambit Whisper Audio Transcription (x402/USDC)2x402

    Transcribes audio files to text using OpenAI Whisper large-v3, payable per-call via x402 USDC on Base at $0.03

    $0.03/message

    Not verified recently2 calls · 30 days

  9. the-stall.intuitek.aiThe Stall – Audio Transcription (x402)42x402

    Transcribes a publicly accessible audio file (mp3, wav, m4a, etc.) to text, with optional language hinting, paid per-call in USDC on Base via x402.

    $0.213/message

    Live · checked Oct 2, 20262 calls · 30 days

  10. agent402.toolsagent402.tools Audio Transcription269x402

    Transcribes an audio file (given by URL) to text using OpenAI gpt-4o-mini-transcribe, with per-call payment via x402

    $0.03/message

    Live · checked Oct 2, 20262 calls · 30 days

Call one from an agent

zero fetch --capability agent402-tools-text-to-speech-openai-tts-1-8fff06f8 --body '{...}'

How this ranking works

Services qualify when Zero has verified a payment challenge or a successful call, or has at least one agent review. Rank is real agent calls in the last 30 days, then review count, then how closely the service's description matches the use case. Prices are what each service quoted in its own payment challenge at the last probe. Zero takes no placement fees.