| name | gemini-tts |
| description | Render text to mp3 via Google Gemini Flash TTS. Free-tier eligible (1500 req/day). Use for video narration, demo voiceovers, audio notes. Parallels openai-tts; default for make-viral-video. |
| user-invocable | true |
Gemini TTS
Synthesize speech via Google's gemini-2.5-flash-preview-tts (or -pro-tts / -lite-preview-tts per env override). Reads GEMINI_API_KEY from .env.
This is offline synthesis — distinct from voice-agent's bidirectional Gemini Live audio. Same model family, different surface (POST text → get audio bytes back, no streaming).
Usage: /gemini-tts [text]
ARGUMENTS: $ARGUMENTS
Voices
Aoede (default — alto, neutral), Charon (baritone, news-anchor), Kore (mid, expressive), Puck (high, conversational). Per Lucy's 2026-05-09 testing: Aoede is the closest match to OpenAI's sage.
Audio tags for expression
Inline bracket tags like [whispers], [excitedly], [slowly] are interpreted as stylistic direction, not spoken literally. Empirically verified against gemini-2.5-flash-preview-tts (per PR #646 comment): [whispers] hello → 1.05s audio; hello alone → 1.01s. If the tag were spoken literally as 8 words, the clip would be ~5× longer.
bash "$SKILL_DIR/scripts/synthesize.sh" -- "[whispers] Pull request 691 has landed."
Model selection
Default: gemini-2.5-flash-preview-tts (free tier, 1500 req/day, $0 within quota).
Override via GEMINI_TTS_MODEL env var:
gemini-2.5-pro-tts — paid, higher fidelitygemini-2.5-flash-lite-preview-tts — preview, fastergemini-3.1-flash-tts-preview — preview
Examples
bash "$SKILL_DIR/scripts/synthesize.sh" -- "Hello, this is Sutando."
bash "$SKILL_DIR/scripts/synthesize.sh" --voice Charon --out /tmp/intro.mp3 -- "Hi."
GEMINI_TTS_MODEL=gemini-2.5-pro-tts bash "$SKILL_DIR/scripts/synthesize.sh" -- "High-fidelity narration."
Default output path: results/gemini-tts-{epoch}.mp3.
Cost
Free tier: $0 within 1500 req/day quota. For our cadence (a few demos a day), stays free indefinitely.
Paid (Flash): $0.50 / 1M input tokens + $10.00 / 1M output tokens.
Compared to OpenAI TTS (gpt-4o-mini-tts) at ~$0.02 per 60s: Gemini Flash is free-equivalent for typical demo workloads.
When to fall back to openai-tts
The make-viral-video skill auto-falls-back to OpenAI TTS when:
- Gemini API returns 4xx/5xx
- Gemini quota hit (429)
GEMINI_API_KEY missingTTS_PROVIDER=OPENAI env override set
If Invoked As A Slash Command
If ARGUMENTS is empty, ask the user for the text. Otherwise:
bash "$SKILL_DIR/scripts/synthesize.sh" -- "$ARGUMENTS"
