ElevenLabs Text to Speech API + MCP vs Rime TTS API + MCP

ElevenLabs Text to Speech API + MCP

Keys can be limited to chosen endpoints and given a credit quota, and service accounts hold keys that don't belong to a person. Content may be used for training unless you opt out under Data use, and the opt-out only applies going forward.

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.

ElevenLabs Text to Speech API + MCP

1. Call Eleven v4 through Text to Dialogue, not /v1/text-to-speech.
2. Spell out numbers yourself on eleven_flash_v2_5, which doesn't normalise them by default, and turning that on is Enterprise only.
3. On 429 read code, back off on rate_limit_exceeded and wait for running requests on concurrent_limit_exceeded.
4. Keep each request under 10,000 characters on v4 and Multilingual v2, 5,000 on v3.
5. Give the agent a key scoped to Text to Speech with a credit quota.

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.