realtime-tts-mcp

An MCP server wrapping ReadAloud's realtime streaming text-to-speech API (Kokoro-82M) as a single synthesize_speech tool. Returns a playable WAV file. Typical warm latency is well under a second.

Tool

• synthesize_speech(text, voice?, speed?) — converts text to spoken audio. voice defaults to af_heart (a Kokoro voice id); speed defaults to 1.0.

Install

npx realtime-tts-mcp

Or from source:

git clone https://github.com/tsushanth/realtime-tts-mcp.git
cd realtime-tts-mcp
npm install
npm run build

Add to your MCP client config:

{
  "mcpServers": {
    "realtime-tts": {
      "command": "npx",
      "args": ["-y", "realtime-tts-mcp"],
      "env": {
        "REALTIME_TTS_API_KEY": "rtts_your_key_here"
      }
    }
  }
}

Getting an API key

Self-serve signup at https://readaloudai.org/developers — sign in with email, generate a key. 10,000 characters free, no card required. Beyond that, pay-as-you-go at $0.01 per 1,000 characters (no plan to manage). Without a key, calls fail with a clear error pointing you to the signup page.

How it works

Each call does two steps: authorize (a fast key + free-tier/billing check against the ReadAloud API) then connects directly to the synthesis worker with a short-lived token — no relay hop in between, which is what keeps warm-call latency well under a second. A cold worker (idle for a couple minutes) can take several seconds longer on the first call after a gap.

Environment variables

| Variable | Default | Purpose | |---|---|---| | REALTIME_TTS_API_KEY | (none, required) | Get one free at https://readaloudai.org/developers | | REALTIME_TTS_API_BASE | https://api.readaloudai.org | API base URL | | REALTIME_TTS_TIMEOUT_MS | 30000 | Per-synthesis timeout |

License

MIT