MCP Chirp 3 HD Server

This tool provides Text-to-Speech (TTS) capabilities using Google Cloud TTS with Chirp3-HD voices. It is one of the MCP tools for Google Cloud Genmedia services, acting as an MCP server component to enable LLMs and other MCP clients to synthesize speech.

MCP Tool Definitions

The following tools are exposed by this server:

1. chirp_tts

• Description: Synthesizes speech from text using Google Cloud TTS with Chirp3-HD voices. Returns audio data and optionally saves it locally.
• Handler: chirpTTSHandler
• Parameters:
  • text (string, required): The text to synthesize into speech.
  • voice_name (string, optional): The specific Chirp3-HD voice name to use (e.g., “en-US-Chirp3-HD-Zephyr”).
    • If not provided, defaults to “en-US-Chirp3-HD-Zephyr” if available, otherwise the first available Chirp3-HD voice.
  • output_filename_prefix (string, optional): A prefix for the output WAV filename if saving locally. A timestamp and .wav extension will be appended.
    • Default: "chirp_audio"
  • output_directory (string, optional): If provided, specifies a local directory to save the generated audio file to. Filenames will be generated automatically using the prefix. If not provided, audio data is returned in the response.
  • pronunciations (array of strings, optional): An array of custom pronunciations. Each item should be a string in the format ‘phrase:phonetic_representation’ (e.g., ‘tomato:təˈmeɪtoʊ’). All items must use the same encoding specified by pronunciation_encoding.
  • pronunciation_encoding (string, optional, enum: “ipa”, “xsampa”): The phonetic encoding used for the pronunciations array.
    • Default: "ipa"

2. list_chirp_voices

• Description: Lists Chirp3-HD voices, filtered by the provided language (either descriptive name or BCP-47 code).
• Handler: listChirpVoicesHandler
• Parameters:
  • language (string, required): The language to filter voices by. Can be a descriptive name (e.g., ‘English (United States)’) or a BCP-47 code (e.g., ‘en-US’).

Environment Variable Configuration

The tool utilizes the following environment variables:

• GOOGLE_CLOUD_PROJECT (string): Required. Your Google Cloud Project ID. The application will terminate if this is not set. Note: PROJECT_ID is also supported as a fallback.
  • Override: You can override this globally for this specific server by setting CHIRP3_PROJECT_ID.
• GOOGLE_CLOUD_LOCATION (string): The preferred Google Cloud region for Chirp3-HD services. Supported regions are: global, us, eu, asia-southeast1, europe-west2, and asia-northeast1.
  • Default: "global" (Note: if you inherit "us-central1" from a generic .env file, the server will automatically map it to "us" or "global" to prevent errors, as Chirp3-HD does not support us-central1).
  • Fallback: LOCATION is also supported as a fallback for GOOGLE_CLOUD_LOCATION.
  • Override: You can override this globally for this specific server by setting CHIRP3_LOCATION.
• PORT (string, for HTTP/SSE transport): The port for the server to listen on if using HTTP or SSE transport.
  • Default for HTTP: "8080" (from getEnv call in main for HTTP).
  • Default for SSE: "8081" (if -p flag is not used and transport is sse). The -p flag can override this.

Transports Supported

• stdio (default)
• sse (Server-Sent Events)
• http (Streamable HTTP)

CORS is enabled for the HTTP transport, allowing all origins by default.

Run

Build the tool using go build or go install.

• STDIO (Default):

  ./mcp-chirp3-go
  # or
  ./mcp-chirp3-go -transport stdio

• HTTP:

  ./mcp-chirp3-go -transport http
  # Optionally set PORT environment variable, e.g., PORT=8082 ./mcp-chirp3-go -transport http

  The MCP server will be available at http://localhost:<PORT>/mcp.
• SSE (Server-Sent Events):

  ./mcp-chirp3-go -transport sse -p <SSE_PORT>
  # Example: ./mcp-chirp3-go -transport sse -p 8081

  The MCP server will be available at http://localhost:<SSE_PORT>.

Examples

List Chirp Voices

{
  "method": "tools/call",
  "params": {
    "name": "list_chirp_voices",
    "arguments": {
      "language": "english (australia)"
    }
  }
}

Chirp TTS Synthesis

{
  "method": "tools/call",
  "params": {
    "name": "chirp_tts",
    "arguments": {
      "text": "Hello from the Model Context Protocol and Chirp3!",
      "voice_name": "en-US-Chirp3-HD-Zephyr",
      "output_directory": "./audio_output"
    }
  }
}