Google · Voice model

Gemini 3.1 Flash TTS Preview

google/gemini-3.1-flash-tts-preview

Voice

Released Apr 24, 2026

Gemini 3.1 Flash TTS Preview is a text-to-speech model from Google, and a substantial generational step up from Gemini 2.5 Flash TTS. It takes text input and produces audio output...

Specifications

Input: text, up to 20,000 characters per call
Output: mp3 (default) or raw pcm
Voice: provider voice ids via `voice`; omitted = the provider's default when it has one
Billing: per input token and audio output token

Use it

POST /api/v1/audio/speech · MCP speak · full reference

curl https://omnirail.org/api/v1/audio/speech \
  -H "Authorization: Bearer $OMNIRAIL_KEY" -H "Content-Type: application/json" \
  -d '{"model":"google/gemini-3.1-flash-tts-preview","input":"Hello from OmniRail. Every model, one key.","response_format":"mp3"}' \
  --output hello.mp3