TonePerfect Pronunciation API - 2026 Pricing, Features, Reviews & Alternatives

TonePerfect Pronunciation API is a cloud-based REST API that scores learner pronunciation across 10 languages — Mandarin Chinese, English, French, Spanish, German, Italian, Portuguese, Russian, Korean, and Japanese — at sentence, word, and sound level. Developers submit a short audio recording and reference text to a single POST endpoint and receive a unified JSON response containing 0-100 scores for the full sentence, every word, and every individual sound. Russian, Korean, and Japanese support is currently in beta. Audio is processed server-side and deleted immediately after scoring; it is never stored or used for model training.

TonePerfect Pronunciation API is designed for developers building language learning apps, pronunciation practice tools, and speaking assessment features. The Mandarin language pack breaks each syllable into its initial, final, and tone components, scoring each independently and estimating the heard value — for example, expected tone 4, heard tone 2, or expected initial "sh," heard "s." Tone sandhi rules (3-3 and bu-4th-tone changes) are handled natively, so correctly applied sandhi is not flagged as an error. The English and French packs add fluency and rhythm dimensions at sentence level alongside expected-versus-heard phoneme data per word. Every scored unit carries a three-way correction decision (review, uncertain, or no_correction) derived from acoustic evidence strength rather than a fixed score threshold, removing the need for developers to configure manual cutoffs.

Operationally, the API exposes one endpoint and one consistent JSON shape across all 10 language packs, reducing integration overhead. Word-level timestamps (start_ms, end_ms) are included on every word, supporting in-app audio replay of specific segments. Idempotency-Key header support prevents double-billing on retried requests, and failed or unassessable requests are not charged. Results are cached for up to 24 hours so retried requests return the same scored response. Accounts receive 50 free credits on creation for live API testing; paid plans start at $10 per month for 2,500 credits, scaling to $150 per month for 50,000 credits.