VOICEVOX TTS MCP

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A text-to-speech MCP server using VOICEVOX

🎮 Try the Browser Demo — Test VoicevoxClient directly in your browser

What You Can Do

• Make your AI assistant speak — Text-to-speech from MCP clients like Claude Desktop
• UI Audio Player (MCP Apps) — Play audio directly in the chat with an interactive player (ChatGPT / Claude Desktop / Claude Web etc.)
• Multi-character conversations — Switch speakers per segment in a single call
• Smooth playback — Queue management, immediate playback, prefetching, streaming
• Cross-platform — Works on Windows, macOS, Linux (including WSL)

UI Audio Player (MCP Apps)

The voicevox_speak_player tool uses MCP Apps to render an interactive audio player directly inside the chat. Unlike the standard voicevox_speak tool which plays audio on the server, audio is played on the client side (in the browser/app) — no audio device needed on the server.

Features

• Client-side playback — Audio plays in Claude Desktop's chat, not on the server. Works even over remote connections.
• Play/Pause controls — Full playback controls embedded in the conversation
• Multi-speaker dialogue — Sequential playback of multiple speakers in one player with track navigation
• Speaker switching — Change the voice of any segment directly from the player UI
• Segment editing — Adjust speed, volume, intonation, pause length, and pre/post silence per segment
• Accent phrase editing — Edit accent positions and mora pitch directly in the UI
• Add / delete / reorder segments — Drag-and-drop track reordering; add new segments inline
• WAV export — Save all tracks as numbered WAV files and open the output folder automatically
• User dictionary manager — Add, edit, and delete VOICEVOX user dictionary words with preview playback
• Cross-session state restore — Player state is persisted on the server; reopening the chat restores previous tracks

Export behavior by environment:

• Save and open always exports WAV files. If opening the file explorer is not supported, export still succeeds and the save path is shown in the UI.
• Choose output folder uses a native directory picker on Windows/macOS. On unsupported environments, this action falls back to the default export directory.

Multi-speaker playback	Track list	Segment editing

Speaker selection	Dictionary manager	WAV export

Supported Clients

Client	Connection	Notes
ChatGPT	HTTP (remote)	Requires VOICEVOX_PLAYER_DOMAIN
Claude Desktop	stdio (local)	Works out of the box
Claude Desktop	HTTP (via mcp-remote)	Do not set VOICEVOX_PLAYER_DOMAIN

Note: speak_player requires a host that supports MCP Apps. In hosts without MCP Apps support, the tool is not available and speak (server-side playback) can be used instead.

Player MCP Tools

Tool	Description
speak_player	Create a new player session and display the UI. Returns viewUUID.
resynthesize_player	Update all segments for an existing player (new viewUUID each call).
get_player_state	Read the current player state (paginated) for AI tuning.
open_dictionary_ui	Open the user dictionary manager UI.

Quick Start

Requirements

• Node.js 18.0.0 or higher (or Bun) or Docker
• VOICEVOX Engine (must be running; included in Docker Compose)
• ffplay (optional, recommended — not needed with Docker)

Installing FFplay

ffplay is a lightweight player included with FFmpeg that supports playback from stdin. When available, it automatically enables low-latency streaming playback.

💡 FFplay is optional. Without it, playback falls back to temp file-based playback (Windows: PowerShell, macOS: afplay, Linux: aplay, etc.).

• Easy setup: One-liner installation for each OS (see steps below)
• Required: ffplay must be in PATH (restart terminal/apps after installation)

FFplay Installation and PATH Setup

Installation examples:

• Windows (any of these)

  • Winget: winget install --id=Gyan.FFmpeg -e
  • Chocolatey: choco install ffmpeg
  • Scoop: scoop install ffmpeg
  • Official builds: Download from https://www.gyan.dev/ffmpeg/builds/ or https://github.com/BtbN/FFmpeg-Builds and add the bin folder to PATH

• macOS

  • Homebrew: brew install ffmpeg

• Linux

  • Debian/Ubuntu: sudo apt-get update && sudo apt-get install -y ffmpeg
  • Fedora: sudo dnf install -y ffmpeg
  • Arch: sudo pacman -S ffmpeg

PATH Setup:

• Windows: Add ...\ffmpeg\bin to environment variables, then restart PowerShell/terminal and editor (Claude/VS Code, etc.)
  • Verify: powershell -c "$env:Path" should include the ffmpeg path
• macOS/Linux: Usually auto-detected. Check with echo $PATH if needed, restart shell.
• MCP clients (Claude Desktop/Code): Restart the app to reload PATH.

Verification:

ffplay -version

If version info is displayed, installation is complete. CLI/MCP will automatically detect ffplay and use stdin streaming playback.

3 Steps to Get Started

1. Start VOICEVOX Engine

2. Add to Claude Desktop config file

Config file location:

• Windows: %APPDATA%\Claude\claude_desktop_config.json
• macOS: ~/Library/Application Support/Claude/claude_desktop_config.json

{
  "mcpServers": {
    "tts-mcp": {
      "command": "npx",
      "args": ["-y", "@kajidog/mcp-tts-voicevox"]
    }
  }
}

💡 If using Bun, just replace npx with bunx:

"command": "bunx", "args": ["@kajidog/mcp-tts-voicevox"]

3. Restart Claude Desktop

That's it! Ask Claude to "say hello" and it will speak!

Quick Start with Docker

You can run both the MCP server and VOICEVOX Engine with a single command using Docker Compose. No Node.js or VOICEVOX installation required.

1. Start the containers

docker compose up -d

This starts the VOICEVOX Engine and the MCP server (HTTP mode on port 3000).

2. Add to Claude Desktop config file (using mcp-remote)

{
  "mcpServers": {
    "tts-mcp": {
      "command": "npx",
      "args": ["-y", "mcp-remote", "http://localhost:3000/mcp"]
    }
  }
}

3. Restart Claude Desktop

Limitations (Docker): The Docker container has no audio device, so the voicevox_speak tool (server-side playback) is disabled by default. Use voicevox_speak_player instead — it plays audio on the client side (in Claude Desktop) and works without any audio device on the server. See UI Audio Player for details.

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MCP Tools

voicevox_speak — Text-to-Speech

The main feature callable from Claude.

Parameter	Description	Default
text	Text to speak (multiple segments separated by newlines)	Required
speaker	Speaker ID	1
speedScale	Playback speed	1.0
immediate	Immediate playback (clears queue)	true
waitForEnd	Wait for playback completion	false

Examples:

// Simple text
{ "text": "Hello" }

// Specify speaker
{ "text": "Hello", "speaker": 3 }

// Different speakers per segment
{ "text": "1:Hello\n3:Nice weather today" }

// Wait for completion (synchronous processing)
{ "text": "Wait for this to finish before continuing", "waitForEnd": true }

Other Tools

Tool	Description
voicevox_speak_player	Speak with UI audio player (disable with --disable-tools)
voicevox_ping	Check VOICEVOX Engine connection
voicevox_get_speakers	Get list of available speakers
voicevox_stop_speaker	Stop playback and clear queue
voicevox_synthesize_file	Generate audio file

---

Configuration

Environment Variables

VOICEVOX Settings

Variable	Description	Default
VOICEVOX_URL	Engine URL	http://localhost:50021
VOICEVOX_DEFAULT_SPEAKER	Default speaker ID	1
VOICEVOX_DEFAULT_SPEED_SCALE	Playback speed	1.0

Playback Options

Variable	Description	Default
VOICEVOX_USE_STREAMING	Streaming playback (requires ffplay)	false
VOICEVOX_DEFAULT_IMMEDIATE	Immediate playback	true
VOICEVOX_DEFAULT_WAIT_FOR_START	Wait for playback start	false
VOICEVOX_DEFAULT_WAIT_FOR_END	Wait for playback end	false

Restriction Settings

Restrict AI from specifying certain options.

Variable	Description
VOICEVOX_RESTRICT_IMMEDIATE	Restrict immediate option
VOICEVOX_RESTRICT_WAIT_FOR_START	Restrict waitForStart option
VOICEVOX_RESTRICT_WAIT_FOR_END	Restrict waitForEnd option

Disable Tools

# Disable individual tools
export VOICEVOX_DISABLED_TOOLS=speak_player,synthesize_file

# Disable a built-in group of tools
export VOICEVOX_DISABLED_GROUPS=player

# Combine groups and individual tools
export VOICEVOX_DISABLED_GROUPS=dictionary
export VOICEVOX_DISABLED_TOOLS=synthesize_file

Built-in groups for VOICEVOX_DISABLED_GROUPS / --disable-groups:

Group	Tools
player	speak_player, resynthesize_player, get_player_state, open_dictionary_ui
dictionary	get_accent_phrases, get_user_dictionary, add_user_dictionary_word, update_user_dictionary_word, delete_user_dictionary_word, add_user_dictionary_words, update_user_dictionary_words
file	synthesize_file
apps	speak_player, resynthesize_player, open_dictionary_ui (MCP App UI tools)

UI Player Settings

Variable	Description	Default
VOICEVOX_PLAYER_DOMAIN	Widget domain for UI player (required for ChatGPT, e.g. https://your-app.onrender.com)	(unset)
VOICEVOX_AUTO_PLAY	Auto-play audio in UI player	true
VOICEVOX_PLAYER_EXPORT_ENABLED	Enable track export(download) from UI player (false to disable)	true
VOICEVOX_PLAYER_EXPORT_DIR	Default output directory for exported tracks (also used as fallback when folder picker is unavailable)	./voicevox-player-exports
VOICEVOX_PLAYER_CACHE_DIR	Directory for player cache files (*.txt) and default player state file	./.voicevox-player-cache
VOICEVOX_PLAYER_AUDIO_CACHE_ENABLED	Enable persistent audio cache on disk (false disables disk cache writes/reads)	true
VOICEVOX_PLAYER_AUDIO_CACHE_TTL_DAYS	Audio cache retention in days (0: disable disk cache, -1: no TTL cleanup)	30
VOICEVOX_PLAYER_AUDIO_CACHE_MAX_MB	Audio cache size cap in MB (0: disable disk cache, -1: unlimited)	512
VOICEVOX_PLAYER_STATE_FILE	Path of persisted player state JSON	<VOICEVOX_PLAYER_CACHE_DIR>/player-state.json

Server Settings

Variable	Description	Default
MCP_HTTP_MODE	Enable HTTP mode	false
MCP_HTTP_PORT	HTTP port	3000
MCP_HTTP_HOST	HTTP host	0.0.0.0
MCP_ALLOWED_HOSTS	Allowed hosts (comma-separated)	localhost,127.0.0.1,[::1]
MCP_ALLOWED_ORIGINS	Allowed origins (comma-separated)	http://localhost,http://127.0.0.1,...
MCP_API_KEY	Required API key for /mcp (sent via X-API-Key or Authorization: Bearer)	(unset)

Command Line Arguments

Command line arguments take priority over environment variables.

# Basic settings
npx @kajidog/mcp-tts-voicevox --url http://192.168.1.100:50021 --speaker 3 --speed 1.2

# HTTP mode
npx @kajidog/mcp-tts-voicevox --http --port 8080

# With restrictions
npx @kajidog/mcp-tts-voicevox --restrict-immediate --restrict-wait-for-end

# Disable individual tools
npx @kajidog/mcp-tts-voicevox --disable-tools speak_player,synthesize_file

# Disable a tool group
npx @kajidog/mcp-tts-voicevox --disable-groups player

Argument	Description
--help, -h	Show help
--version, -v	Show version
--init	Generate .voicevoxrc.json with default settings
--config <path>	Path to config file
--url <value>	VOICEVOX Engine URL
--speaker <value>	Default speaker ID
--speed <value>	Playback speed
--use-streaming / --no-use-streaming	Streaming playback
--immediate / --no-immediate	Immediate playback
--wait-for-start / --no-wait-for-start	Wait for start
--wait-for-end / --no-wait-for-end	Wait for end
--restrict-immediate	Restrict immediate
--restrict-wait-for-start	Restrict waitForStart
--restrict-wait-for-end	Restrict waitForEnd
--disable-tools <tools>	Disable tools (comma-separated tool names)
--disable-groups <groups>	Disable tool groups: player, dictionary, file, apps
--auto-play / --no-auto-play	Auto-play in UI player
--player-export / --no-player-export	Enable/disable track export(download) in UI player
--player-export-dir <dir>	Default output directory for exported tracks
--player-cache-dir <dir>	Player cache directory
--player-state-file <path>	Persisted player state file path
--player-audio-cache / --no-player-audio-cache	Enable/disable disk audio cache for player
--player-audio-cache-ttl-days <days>	Audio cache retention days (0: disable, -1: no TTL cleanup)
--player-audio-cache-max-mb <mb>	Audio cache size cap in MB (0: disable, -1: unlimited)
--http	HTTP mode
--port <value>	HTTP port
--host <value>	HTTP host
--allowed-hosts <hosts>	Allowed hosts (comma-separated)
--allowed-origins <origins>	Allowed origins (comma-separated)
--api-key <key>	Required API key for /mcp

Config File (.voicevoxrc.json)

You can use a JSON config file instead of (or in addition to) environment variables and CLI arguments. This is useful when you have many settings to configure.

Priority order: CLI args > Environment variables > Config file > Defaults

Generate a config file

npx @kajidog/mcp-tts-voicevox --init

This creates .voicevoxrc.json in the current directory with all default settings. Edit it as needed.

Use a custom config file path

npx @kajidog/mcp-tts-voicevox --config ./my-config.json

Or via environment variable:

VOICEVOX_CONFIG=./my-config.json npx @kajidog/mcp-tts-voicevox

Example .voicevoxrc.json

{
  "url": "http://192.168.1.50:50021",
  "speaker": 3,
  "speed": 1.2,
  "http": true,
  "port": 8080,
  "disable-tools": ["synthesize_file"],
  "disable-groups": ["dictionary"]
}

Keys can be written in kebab-case (use-streaming), camelCase (useStreaming), or internal key names (defaultSpeaker). If .voicevoxrc.json exists in the current directory, it is loaded automatically.

HTTP Mode

For remote connections:

Start Server:

# Linux/macOS
MCP_HTTP_MODE=true MCP_HTTP_PORT=3000 npx @kajidog/mcp-tts-voicevox

# Windows PowerShell
$env:MCP_HTTP_MODE='true'; $env:MCP_HTTP_PORT='3000'; npx @kajidog/mcp-tts-voicevox

Claude Desktop Config (using mcp-remote):

{
  "mcpServers": {
    "tts-mcp-proxy": {
      "command": "npx",
      "args": ["-y", "mcp-remote", "http://localhost:3000/mcp"]
    }
  }
}

Per-Project Speaker Settings

With Claude Code, you can configure different default speakers per project using custom headers in .mcp.json:

Header	Description
X-Voicevox-Speaker	Default speaker ID for this project
X-API-Key	API key when MCP_API_KEY is configured

Example .mcp.json:

{
  "mcpServers": {
    "tts": {
      "type": "http",
      "url": "http://localhost:3000/mcp",
      "headers": {
        "X-Voicevox-Speaker": "113",
        "X-API-Key": "your-api-key"
      }
    }
  }
}

This allows each project to use a different voice character automatically.

Priority order:

1. Explicit speaker parameter in tool call (highest)
2. Project default from X-Voicevox-Speaker header
3. Global VOICEVOX_DEFAULT_SPEAKER setting (lowest)

WSL to Windows Host Connection

Connecting from WSL to an MCP server running on Windows:

1. Get Windows Host IP from WSL

# Method 1: From default gateway
ip route show | grep -oP 'default via \K[\d.]+'
# Usually in the format 172.x.x.1

# Method 2: From /etc/resolv.conf (WSL2)
cat /etc/resolv.conf | grep nameserver | awk '{print $2}'

2. Start Server on Windows

Add the WSL gateway IP to MCP_ALLOWED_HOSTS to allow access from WSL:

$env:MCP_HTTP_MODE='true'
$env:MCP_ALLOWED_HOSTS='localhost,127.0.0.1,172.29.176.1'
npx @kajidog/mcp-tts-voicevox

Or with CLI arguments:

npx @kajidog/mcp-tts-voicevox --http --allowed-hosts "localhost,127.0.0.1,172.29.176.1"

3. WSL Configuration (.mcp.json)

{
  "mcpServers": {
    "tts": {
      "type": "http",
      "url": "http://172.29.176.1:3000/mcp"
    }
  }
}

⚠️ Within WSL, localhost refers to WSL itself. Use the WSL gateway IP to access the Windows host.

Using with ChatGPT

To use with ChatGPT, deploy the MCP server in HTTP mode to the cloud with access to a VOICEVOX Engine.

1. Deploy to the Cloud

Deploy with Docker to Render, Railway, etc. (Dockerfile included).

2. Set Up VOICEVOX Engine

Run VOICEVOX Engine locally and expose it via ngrok, or deploy it alongside the MCP server.

3. Configure Environment Variables

Variable	Example	Description
VOICEVOX_URL	https://xxxx.ngrok-free.app	VOICEVOX Engine URL
MCP_HTTP_MODE	true	Enable HTTP mode
MCP_ALLOWED_HOSTS	your-app.onrender.com	Deployed hostname
VOICEVOX_PLAYER_DOMAIN	https://your-app.onrender.com	Widget domain for UI player (required for ChatGPT)
VOICEVOX_DISABLED_TOOLS	speak	Disable server-side playback (no audio device)
VOICEVOX_PLAYER_EXPORT_ENABLED	false	Disable export feature (files cannot be downloaded from cloud)

4. Add Connector in ChatGPT

Go to ChatGPT Settings → Connectors → Add MCP server URL (https://your-app.onrender.com/mcp).

Using with Claude Web

The basic steps are the same as ChatGPT, but the VOICEVOX_PLAYER_DOMAIN value is different.

Claude Web requires ui.domain to be a hash-based dedicated domain. Compute it with the following command:

node -e "console.log(require('crypto').createHash('sha256').update('Your MCP server URL').digest('hex').slice(0,32)+'.claudemcpcontent.com')"

Example: If your MCP server URL is https://your-app.onrender.com/mcp:

node -e "console.log(require('crypto').createHash('sha256').update('https://your-app.onrender.com/mcp').digest('hex').slice(0,32)+'.claudemcpcontent.com')"
# Example output: 48fb73a6...claudemcpcontent.com

Set this output value as VOICEVOX_PLAYER_DOMAIN.

Note: Since ChatGPT and Claude Web require different VOICEVOX_PLAYER_DOMAIN values, a single instance cannot serve both clients simultaneously. Deploy separate instances for each, or switch the environment variable depending on your target client.

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Troubleshooting

Audio is not playing

1. Check if VOICEVOX Engine is running

curl http://localhost:50021/speakers

2. Check platform-specific playback tools

OS	Required Tool
Linux	One of aplay, paplay, play, ffplay
macOS	afplay (pre-installed)
Windows	PowerShell (pre-installed)

Not recognized by MCP client

• Check package installation: npm list -g @kajidog/mcp-tts-voicevox
• Verify JSON syntax in config file
• Restart the client

---

Package Structure

Package	Description
@kajidog/mcp-tts-voicevox	MCP server
@kajidog/voicevox-client	General-purpose VOICEVOX client library (can be used independently)
@kajidog/player-ui	React-based audio player UI for browser playback

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Developer Information

Setup

git clone https://github.com/kajidog/mcp-tts-voicevox.git
cd mcp-tts-voicevox
pnpm install

Commands

Command	Description
pnpm build	Build all packages
pnpm test	Run tests
pnpm lint	Run lint
pnpm dev	Start dev server
pnpm dev:stdio	Dev with stdio mode
pnpm dev:bun	Start dev server with Bun
pnpm dev:bun:http	Start HTTP dev server with Bun

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License

ISC