speak-mcp

An MCP server for text-to-speech generation using Gemini TTS and local Irodori-TTS.

speak-mcp lets MCP clients such as Codex, Claude Code, and Claude Desktop ask a tool to turn text into a local .wav file and play it immediately. It is designed for open-source use: API keys stay in environment variables, output paths are sandboxed, and generated speech text is not logged by the server.

Providers & Models

Gemini

Name	Model ID	Best for
`gemini-3.1-flash-tts`	`gemini-3.1-flash-tts-preview`	Fast, controllable text-to-speech

Irodori-TTS

Mode	Checkpoint	Best for
`reference`	`Aratako/Irodori-TTS-500M-v2`	Generate speech from a fixed reference voice profile
`voice_design`	`Aratako/Irodori-TTS-500M-v2-VoiceDesign`	Generate speech from a style prompt/caption

Built-in reference profile:

Profile	Reference audio
`franca`	`assets/profiles/franca-reference.wav` (in the source repo; not bundled in the npm tarball)

Requirements

Node.js 20+
macOS (local playback uses afplay; audio generation works on Linux and Windows but local playback does not)
A Gemini API key for provider: "gemini"
uv and a local Irodori-TTS checkout for provider: "irodori"

Installation

npx speak-mcp

Or install globally:

npm install -g speak-mcp

Quick start

The fastest path to a working install is the Gemini provider with one environment variable:

export GEMINI_TTS_API_KEY=your_key_here
npx speak-mcp

Then have your MCP client call the speak_text tool with provider: "gemini" (the default). A .wav file is written under SPEAK_MCP_OUTPUT_DIR (default ~/speak-mcp-output) and played via afplay on macOS.

The Irodori provider needs additional setup (a local checkout of Irodori-TTS with infer.py, plus a reference WAV). See Irodori reference profiles below.

Setup

Set a Gemini API key:

export GEMINI_TTS_API_KEY=your_key_here

Optional output and voice defaults:

export SPEAK_MCP_OUTPUT_DIR="$HOME/speak-mcp-output"
export SPEAK_MCP_DEFAULT_VOICE=Zephyr
export SPEAK_MCP_STYLE_PROMPT="Warm, concise, and calm. Speak naturally, like a close colleague."
# or
export SPEAK_MCP_DEFAULT_VOICE=Leda
export SPEAK_MCP_IRODORI_REPO=/path/to/Irodori-TTS

Claude Desktop

Add to your claude_desktop_config.json:

{
  "mcpServers": {
    "speak-mcp": {
      "command": "npx",
      "args": ["speak-mcp"],
      "env": {
        "GEMINI_TTS_API_KEY": "${GEMINI_TTS_API_KEY}",
        "SPEAK_MCP_OUTPUT_DIR": "/path/to/audio/output",
        "SPEAK_MCP_DEFAULT_VOICE": "Zephyr"
      }
    }
  }
}

Codex

If your API key lives in ~/.zshrc, use the bundled launcher so Codex can read it without putting the key in ~/.codex/config.toml:

codex mcp add speak-mcp \
  --env SPEAK_MCP_OUTPUT_DIR="${HOME}/speak-mcp-output" \
  --env SPEAK_MCP_DEFAULT_VOICE=Zephyr \
  -- /path/to/speak-mcp/scripts/codex-launcher.zsh

The launcher sources ~/.zshrc with stdout redirected away from the MCP protocol, then starts dist/index.js. Replace /path/to/speak-mcp with your local clone.

Environment Variables

Variable	Required	Description
`GEMINI_TTS_API_KEY`	Yes	Gemini API key dedicated to TTS. Takes precedence over the fallback variables.
`GEMINI_API_KEY`	No	Fallback Gemini API key variable
`GOOGLE_API_KEY`	No	Fallback Gemini API key variable
`SPEAK_MCP_OUTPUT_DIR`	No	Base directory for saved audio. All output paths are sandboxed within this directory.
`SPEAK_MCP_DEFAULT_VOICE`	No	Default voice for `speak_text`. Defaults to `Zephyr`; `Leda` is also a recommended default.
`SPEAK_MCP_STYLE_PROMPT`	No	Shared voice and delivery instructions applied to every `speak_text` call.
`SPEAK_MCP_STYLE_PROMPT_FILE`	No	Path to a text file containing shared voice and delivery instructions. Used when `SPEAK_MCP_STYLE_PROMPT` is unset.
`SPEAK_MCP_KEEP_AUDIO`	No	Set to `1` to keep generated files after playback by default.
`SPEAK_MCP_DISABLE_PLAYBACK`	No	Set to `1` to save audio without playing it by default.
`SPEAK_MCP_IRODORI_REPO`	Yes (for `provider: "irodori"`)	Path to a local Irodori-TTS checkout containing `infer.py`. Required when `provider: "irodori"` is used.
`SPEAK_MCP_IRODORI_FRANCA_REF_WAV`	No	Optional override for the built-in `franca` reference WAV.
`SPEAK_MCP_IRODORI_FRANCA_CHECKPOINT`	No	Optional override for the `franca` profile checkpoint. Must start with `Aratako/Irodori-TTS-`.

Tool: `speak_text`

Parameters

Parameter	Type	Default	Description
`text`	`string` (1-32,000 chars)	-	Text to synthesize
`provider`	`"gemini"` or `"irodori"`	`"gemini"`	Speech provider
`mode`	`"reference"` or `"voice_design"`	inferred	Irodori mode
`model`	`"gemini-3.1-flash-tts"`	`"gemini-3.1-flash-tts"`	TTS model to use
`voice`	Gemini voice name	`SPEAK_MCP_DEFAULT_VOICE` or `"Zephyr"`	Prebuilt voice name
`outputDir`	`string`	`"."`	Directory where audio will be saved, relative to `SPEAK_MCP_OUTPUT_DIR`
`play`	`boolean`	`true`	Play the generated audio after saving it
`keepFiles`	`boolean`	`false`	Keep generated audio files after playback
`stylePrompt`	`string`	-	Gemini voice instructions, or Irodori `voice_design` caption
`profile`	`string`	`"franca"`	Irodori reference profile
`refWav`	`string`	profile ref	Irodori reference WAV override
`numSteps`	`number`	`20`	Irodori sampling steps (1-120)
`seconds`	`number`	provider default	Irodori target duration in seconds (1-120)
`seed`	`number`	random	Irodori sampling seed
`modelDevice`	`"mps"`, `"cpu"`, `"cuda"`	`"mps"`	Irodori model device
`codecDevice`	`"mps"`, `"cpu"`, `"cuda"`	`"mps"`	Irodori codec device
`modelPrecision`	`"fp32"`, `"bf16"`	`"fp32"`	Irodori model precision
`codecPrecision`	`"fp32"`, `"bf16"`	`"fp32"`	Irodori codec precision

Style prompts

Use a shared prompt to shape tone without repeating it in every call:

export SPEAK_MCP_STYLE_PROMPT="Warm, concise, and calm. Sound like a close colleague, not a narrator."

For longer instructions:

export SPEAK_MCP_STYLE_PROMPT_FILE="$HOME/.config/speak-mcp/style.txt"

Per-call stylePrompt is appended after the shared prompt.

Irodori reference mode

Use the built-in franca voice profile:

{
  "provider": "irodori",
  "mode": "reference",
  "profile": "franca",
  "text": "今日は急がず、ひとつずつ確かめながら進めていきましょう。",
  "play": true
}

The franca profile expects a reference WAV file at assets/profiles/franca-reference.wav inside the source repository. The WAV is not included in the npm tarball to keep the package small. To use the franca profile, set SPEAK_MCP_IRODORI_FRANCA_REF_WAV to a local path:

export SPEAK_MCP_IRODORI_FRANCA_REF_WAV=/path/to/franca-reference.wav

You can either clone this repository and reuse assets/profiles/franca-reference.wav, or supply your own reference WAV. See assets/profiles/README.md in the repository for details.

Irodori VoiceDesign mode

In VoiceDesign mode, stylePrompt is passed to Irodori-TTS as --caption:

{
  "provider": "irodori",
  "mode": "voice_design",
  "text": "今日は少しゆっくり話してみます。",
  "stylePrompt": "若い日本人女性の声。少し低めで気だるげ。近い距離で自然に話す。",
  "play": true
}

Single-request generation

speak_text issues a single TTS request for the full input text. This preserves prosody and tone across the whole utterance.

Cleanup

Generated audio is deleted after successful playback by default. To keep files:

{
  "text": "Keep this one.",
  "keepFiles": true
}

Or set:

export SPEAK_MCP_KEEP_AUDIO=1

Recommended voices

Zephyr - bright
Leda - youthful

Gemini TTS supports 30 prebuilt voices including Zephyr, Puck, Kore, Leda, Aoede, Achird, and Sulafat.

Response

Returns a JSON object:

{
  "model": "gemini-3.1-flash-tts-preview",
  "voice": "Zephyr",
  "savedFile": "/path/to/audio/1760000000000-ab12cd34.wav",
  "savedFiles": ["/path/to/audio/1760000000000-ab12cd34.wav"],
  "deletedFiles": ["/path/to/audio/1760000000000-ab12cd34.wav"],
  "format": "wav",
  "played": true,
  "keptFiles": false,
  "audio": {
    "sampleRate": 24000,
    "channels": 1,
    "bitsPerSample": 16
  }
}

Tool: `play_audio`

Plays an existing generated audio file under SPEAK_MCP_OUTPUT_DIR.

Parameter	Type	Description
`filePath`	`string`	Path to a generated audio file under `SPEAK_MCP_OUTPUT_DIR`

Playback currently uses afplay, so local playback is macOS-only. On Linux and Windows, audio generation works but playback is not yet supported. Set SPEAK_MCP_DISABLE_PLAYBACK=1 (or pass play: false per call) to suppress playback attempts on those platforms.

Why not the Live API?

Gemini TTS is for exact text recitation and controlled speech output. The Gemini Live API is better for interactive, unstructured audio conversations. MCP clients usually need a deterministic "read this text aloud and save the file" tool, so this server starts with TTS and keeps Live API support as a future extension.

Security

Path sandboxing: all audio is written under SPEAK_MCP_OUTPUT_DIR or the default ~/speak-mcp-output. Path traversal and symlinks that escape the sandbox are rejected.
Secret handling: API keys are read only from environment variables. Do not commit .env files.
No prompt logging: the server does not log the input text, generated audio data, or API keys.
Explicit output: audio is saved to disk and only metadata plus the saved path are returned to the MCP client.
Default playback: speak_text plays generated audio by default. Set play: false per call or SPEAK_MCP_DISABLE_PLAYBACK=1 globally to disable playback.
Default cleanup: generated files are deleted after successful playback unless keepFiles: true or SPEAK_MCP_KEEP_AUDIO=1 is set.
AI voice disclosure: applications using generated speech should clearly disclose that users are hearing AI-generated audio.

Development

npm install
npm test

References

Gemini API speech generation: https://ai.google.dev/gemini-api/docs/speech-generation

License

MIT

Name		Name	Last commit message	Last commit date
Latest commit History 5 Commits
assets/profiles		assets/profiles
docs		docs
scripts		scripts
src		src
tests		tests
.env.example		.env.example
.gitignore		.gitignore
CHANGELOG.md		CHANGELOG.md
LICENSE		LICENSE
README.md		README.md
SECURITY.md		SECURITY.md
package-lock.json		package-lock.json
package.json		package.json
server.json		server.json
tsconfig.json		tsconfig.json
tsconfig.test.json		tsconfig.test.json

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speak-mcp

Providers & Models

Gemini

Irodori-TTS

Requirements

Installation

Quick start

Setup

Claude Desktop

Codex

Environment Variables

Tool: `speak_text`

Parameters

Style prompts

Irodori reference mode

Irodori VoiceDesign mode

Single-request generation

Cleanup

Recommended voices

Response

Tool: `play_audio`

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speak-mcp

Providers & Models

Gemini

Irodori-TTS

Requirements

Installation

Quick start

Setup

Claude Desktop

Codex

Environment Variables

Tool: speak_text

Parameters

Style prompts

Irodori reference mode

Irodori VoiceDesign mode

Single-request generation

Cleanup

Recommended voices

Response

Tool: play_audio

Why not the Live API?

Security

Development

References

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About

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