GoogleFastHigh

Gemini 3.8 Flash TTS

Google Gemini 3.8 Flash TTS via Fal.AI. Expressive single-speaker narration with 30 prebuilt voices, delivery directions given as separate style instructions, and inline vocal events such as <laugh> and <sigh>. Returns WAV audio.

105 credits

per 1000 characters of spoken text (0.104625 credits/char; style instructions not billed)

30 prebuilt Gemini voices

Style instructions separate from the spoken text — and not billed

Inline vocal events such as <laugh> and <sigh>

Billed only on the characters actually spoken

Run it right now

Test this model instantly in the Console Playground — no code required

Use with AI Assistant

Copy usage instructions for Claude, ChatGPT, or other AI

llms.txtllms.txt ↗

Quick Start

curl -X POST "https://api.core.today/v1/predictions" \
  -H "Content-Type: application/json" \
  -H "X-API-Key: cdt_your_api_key" \
  -d '{
  "model": "google/gemini-3.8-flash-tts",
  "input": {
    "prompt": "Have a wonderful day!",
    "style_instructions": "cheerful and friendly",
    "voice": "Kore"
  }
}'

Parameters

Parameter	Type	Required	Default	Description
`prompt`	string	Yes	-	Verbatim text to speak (billed per character). Put delivery directions in style_instructions; inline vocal events may use <laugh> or <sigh>. The complete input is limited to 8,192 tokens.
`style_instructions`	string	No	-	Delivery style, separate from the spoken transcript (e.g. "cheerful and friendly"). Not billed.
`voice`	string	No	Kore	Prebuilt voice for single-speaker speech. AchernarAchirdAlgenibAlgiebaAlnilamAoedeAutonoeCallirrhoeCharonDespinaEnceladusErinomeFenrirGacruxIapetusKoreLaomedeiaLedaOrusPulcherrimaPuckRasalgethiSadachbiaSadaltagerSchedarSulafatUmbrielVindemiatrixZephyrZubenelgenubi

Common Parameters

Common parameters used when calling POST /v1/predictions.

Parameter	Type	Required	Default	Description
`model`	string	Yes	-	Model identifier
`input`	object	Yes	-	Object containing the model-specific parameters from the table above
`output_folder`	string	No	-	Folder path for output files (max 256 chars, '..' not allowed)
`webhook_url`	string	No	-	Webhook URL to call on completion
`is_public`	boolean	No	false	If true, output files are also available via permanent public URLs

Examples

Cheerful sign-off

A short line with a cheerful, friendly style instruction.

curl -X POST "https://api.core.today/v1/predictions" \
  -H "Content-Type: application/json" \
  -H "X-API-Key: cdt_your_api_key" \
  -d '{
  "model": "google/gemini-3.8-flash-tts",
  "input": {
    "prompt": "Have a wonderful day!",
    "style_instructions": "cheerful and friendly",
    "voice": "Kore"
  }
}'

Calm Korean documentary narration

Korean narration directed to sound slow and calm.

curl -X POST "https://api.core.today/v1/predictions" \
  -H "Content-Type: application/json" \
  -H "X-API-Key: cdt_your_api_key" \
  -d '{
  "model": "google/gemini-3.8-flash-tts",
  "input": {
    "prompt": "깊은 바다 아래, 빛이 닿지 않는 곳에서도 생명은 조용히 이어집니다.",
    "style_instructions": "calm, slow documentary narration with a warm low voice",
    "voice": "Charon"
  }
}'