Resemble AI Text-to-Speech API vs Rime TTS API + MCP

Resemble AI Text-to-Speech API

OpenAPI file in JSON and YAML, llms.txt and Markdown pages. Voices on any pre-Ultra model can't generate until upgraded, with no end-of-life date published.

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.

Resemble AI Text-to-Speech API

1. Check the voice's model before synthesis, since voices on pre-Ultra models fail until upgraded.
2. Keep each synchronous request under 2,000 characters.
3. Decode audio_content from base64 on /synthesize, or call /stream for raw WAV chunks.
4. Send Authorization: Bearer, since some doc examples leave out the prefix.
5. Log the request ID with every failure, since the error body has no code.

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.