# Theta One AI Developer Documentation

> Theta One AI is a REST Speech AI API. The two product lines are Speech-to-Text (STT, including child speech and Korean-English code-switching) and Pronunciation Feedback (native-compared or text-only). All endpoints are synchronous HTTPS, authenticated via the `x-api-key` header, with keys prefixed `sk-theta-`. Base URL: `https://stt.thetaone-ai.com`. There is no official SDK.

## Start here

- [Overview](https://docs.thetaone-ai.com/): landing page and quickstart snippet
- [Quickstart](https://docs.thetaone-ai.com/guides/quickstart): make your first API call in 5 minutes, with cURL / Python / Node.js
- [Choosing an API](https://docs.thetaone-ai.com/guides/choosing-an-api): decision tree for `/transcribe` vs `/pronunciation` vs `/pronunciation-simple`
- [Guide for AI Coding Agents](https://docs.thetaone-ai.com/guides/ai-agents): canonical facts and do/don't rules for code generators

## API reference

- [API Reference Overview](https://docs.thetaone-ai.com/api-reference/overview): base URL, auth, endpoints table, request format, constraints
- [Error Reference](https://docs.thetaone-ai.com/api-reference/errors): 400 / 401 / 402 / 429 / 500 with causes and client reactions
- [Rate Limits & Retries](https://docs.thetaone-ai.com/api-reference/rate-limits): per-key RPM by plan and exponential-backoff recipe

## Endpoints

- [POST /transcribe](https://docs.thetaone-ai.com/apis/transcribe): Speech-to-Text with Korean-English code-switching
- [STT additional features](https://docs.thetaone-ai.com/apis/stt-additional-features): `transcribe_options` (e.g., `suppress_korean`)
- [POST /analyze-native + POST /pronunciation](https://docs.thetaone-ai.com/apis/pronunciation): full pronunciation feedback with native reference (pronunciation / stress / pause / speed)
- [POST /pronunciation-simple](https://docs.thetaone-ai.com/apis/pronunciation-simple): pronunciation score from reference text only, no native audio

## Authentication

- [API Keys](https://docs.thetaone-ai.com/authentication/api-keys): create, use, test, rotate, deactivate

## Console and billing

- [Sign Up](https://docs.thetaone-ai.com/console/signup): create a console account
- [Subscription Plans](https://docs.thetaone-ai.com/billing/overview): Free, Starter, Pro, Enterprise
- [Pricing](https://docs.thetaone-ai.com/billing/pricing): `$0.0004/sec` STT, `$0.0006/sec` Pronunciation
- [Prepaid Credits](https://docs.thetaone-ai.com/billing/prepaid-charging): top-up via Stripe (min `$10`), monthly credits, expiration rules
- [Postpaid Billing](https://docs.thetaone-ai.com/billing/postpaid-charging): Enterprise-only monthly invoice

## Support

- [FAQ](https://docs.thetaone-ai.com/faq)
- Email: support@thetaone.co

## Optional

- [llms-full.txt](https://docs.thetaone-ai.com/llms-full.txt): single-file concatenation of the canonical pages above for retrieval / embedding pipelines