Speech-To-Text (STT) responses can include a confidence score, which can help you assess how successful the transcription is. High-quality audios will result in better performance. However, even with high-quality audio files, some errors may occur. Therefore, you should consider including a confirmation step in your process to guarantee all information is accurate.
For Text-To-Speech (TTS) functionality, you can expect fewer errors when the expressions are well-written. However, you may find that the standard voice used to generate audio is not to your liking.
To discuss how you can obtain even better results, contact Sinch or if you are an existing customer contact your Sinch Account Manager.