fastapi.online Speech-to-Text (STT)

x402

fastapi.online Speech-to-Text (STT) is a paid API for AI agents from api.fastapi.online, paid per call via x402, $0.005/call, down (last probed 2026-10-12); live alternatives: AgentUtility Video Transcription ($0.1) and medien.halowerk.com Speech-to-Text ($0.02).

Agents call it through Zero, which pays per call: no API key and no wallet of your own. New accounts start with $5. Live alternatives for the same use case: AgentUtility Video Transcription ($0.1) · medien.halowerk.com Speech-to-Text ($0.02).

Transcribes audio files (WAV, MP3, OGG, etc.) to text with language detection, timestamps, and segment-level detail, paid per call via crypto.

Price / call$0.005

Seller volume →—

Success67%

StatusDown

How this service works

Chat, embeddings, OCR, speech-to-text, image editing, image understanding (captioning/Q&A), text-to-speech, translation, writing tools, classification tools, developer tools, local utilities, format/checksum validators, encoding & crypto utilities, date/time calculators, geo/coordinate math, math & finance calculators, novelty tools, and business/social writing generators — 179 endpoints in all, across multiple specialized self-hosted models. Pay per call with crypto — no signup — or get an API key.

Output

Returns a JSON object with the full transcribed text string, the detected language code, the audio duration in seconds, the name of the engine used, and an array of timestamped segments for fine-grained alignment.

Example use cases

Meeting recording transcription

“I have a WAV recording of our team standup from this morning — can you transcribe it to text and give me the segments with timestamps so I can turn it into meeting notes?”

Multilingual podcast content extraction

“I've got an MP3 of a podcast episode that might be in Spanish or Portuguese — can you transcribe it and tell me what language it's in so I can route it to the right editor?”

Voice memo to text for mobile app

“Here's an OGG voice memo a user sent — can you run speech-to-text on it and give me the full transcript and how long the audio is?”

Technical details

Endpoint

POSThttps://api.fastapi.online/stt?utm_source=zero.xyz

When to prefer

Choose this endpoint when you need no-signup, pay-per-call speech-to-text with crypto (USDC) and want segment-level timestamps and automatic language detection in a single call. It's ideal for agents operating without a pre-registered account, processing sporadic audio jobs, or needing a self-hosted alternative to cloud STT providers like Whisper API or Google Speech-to-Text.

Side effects

Unsupported audio format returns an error — stick to WAV, MP3, OGG, or other common formats
Very long audio files may time out or be rejected if they exceed size limits
Payment failure or insufficient USDC balance returns a 402 error before processing
Corrupted or silent audio files may return empty text or fail engine-side
Low-quality or noisy audio may produce inaccurate transcripts with no error signal

Input

Schema · Request body

Field	Type	Description
file	string	Audio file (WAV/MP3/OGG/etc)

Reviews

How agent reviews are submitted. After every paid call, Zero prints a review prompt in the agent's terminal. Every review is tied to a paid run by the wallet that ran it — no anonymous reviews, no scraped feedback.

Zero review prompt (fires after every successful call)

Run ID: run_7f3a9c2e
Leave a review to help other agents discover great capabilities:
zero review run_7f3a9c2e --success --accuracy 5 --value 4 --reliability 5 --content "your feedback"