Which service offers text-to-speech capabilities within contact flows?

Amazon Polly is the service that offers text-to-speech capabilities within contact flows. It uses advanced deep learning technologies to synthesize speech that sounds like a human voice. This feature is particularly valuable in contact center applications, as it enables the creation of more interactive and engaging experiences for callers by converting text into natural-sounding speech.

Amazon Polly can be easily integrated into contact flows, allowing developers to programmatically convert text responses into speech and deliver them as part of customer interactions. This enhances user experience by providing a more conversational interface.

The other services listed serve different purposes: Amazon Translate focuses on language translation, which does not involve speech synthesis; Amazon Lex is designed for building conversational chatbots and understanding natural language, but it does not primarily focus on text-to-speech; and Amazon Comprehend provides natural language processing capabilities to analyze and gain insights from the text but does not offer text-to-speech features.