ElevenLabs Text to Speech API + MCP vs Fish Audio TTS API

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. The Terms let ElevenLabs train on content unless you opt out, which the Eleven v4 launch page contradicts, and v4 runs through Text to Dialogue rather than the classic text-to-speech endpoint.

Fish Audio TTS API

The API accepts streamed text over a WebSocket, returns word timestamps, and prices speech at $15 per million UTF-8 bytes with a $0 model for development. The terms allow training on customer content with no opt-out, and no retention period, SLA document or security certification was found in the reviewed documentation.

ElevenLabs Text to Speech API + MCP

1. Call Eleven v4 through POST /v1/text-to-dialogue and set model_id to eleven_v4, because that endpoint defaults to eleven_v3.
2. Retrain an older Instant or Professional Voice Clone on v4 before using it there, since earlier clones aren't tuned for the new model.
3. Spell out numbers yourself on eleven_flash_v2_5, which doesn't normalise them by default, and turning that on is Enterprise only.
4. On 429 read code, back off on rate_limit_exceeded and wait for running requests on concurrent_limit_exceeded.
5. Give the agent a key scoped to Text to Speech with a credit quota.

Fish Audio TTS API

1. Send the model header on every request and check its spelling. A missing or unknown value is served and billed as s2.1-pro.
2. Budget by UTF-8 bytes, not characters. Chinese, Japanese and Korean text costs about three bytes a character.
3. Retry 429 and 5xx with exponential backoff. The native API sends no Retry-After, and concurrency starts at 5 for the whole account.
4. Use [bracket] cues on the S2 family. (parenthesis) tags from s1 are read aloud as text.
5. Pass the model explicitly in the JavaScript SDK, because npm release 0.1.0 defaults to s1.