Amazon Polly vs Rime TTS API + MCP

Amazon Polly

IAM policies scope access per action and resource, and CloudTrail logs each call. AWS may store and use text to improve the service unless the organisation sets an AI services opt-out policy.

Rime TTS API + MCP

Only character counts are kept by default, and customer data isn't used for training without an opt-in. No OpenAPI or AsyncAPI file and no official SDKs.

Amazon Polly

1. Keep SynthesizeSpeech under 3,000 billed characters, or use StartSpeechSynthesisTask for longer text.
2. Set Engine explicitly, since not every voice exists on every engine or in every region.
3. Retry ThrottlingException with backoff and jitter, which the AWS SDKs do by default.
4. Check the generative SSML tag list before porting neural SSML.
5. Ask for OutputFormat json with speech marks when you need word timings.

Rime TTS API + MCP

1. Always send modelId, since a missing one routes to Mist v3 and Coda speakers then fail.
2. Keep HTTP requests under 1,000 characters or use the WebSocket.
3. Back off on 429 before reopening a WebSocket, and remember each retry bills again.
4. Use /ws3 when you need word timestamps.
5. Keep the key server-side, since WebSockets take it in a header and there are no short-lived tokens.