Letterbox MCP Server

What the code does

We read the source, 4 h ago · rules 3dff92dd89df

What this server is able to do. For an MCP server this is often the job itself — a terminal server runs commands because that is what it is for. Listed so you know what you are plugging in, not as an accusation.

        process = subprocess.Popen(

Is this your server and something here is wrong? Tell us — corrections are free and do not require a plan.

Connect this server

This server runs on your own machine — install it with the package manager and the client starts it for you. Package name taken from the official registry entry.

claude mcp add letterbox -- uvx letterbox

{
  "mcpServers": {
    "letterbox": {
      "args": [
        "letterbox"
      ],
      "command": "uvx"
    }
  }
}

[mcp_servers.letterbox]
command = "uvx"
args = ["letterbox"]

{
  "mcpServers": {
    "letterbox": {
      "args": [
        "letterbox"
      ],
      "command": "uvx"
    }
  }
}

{
  "mcpServers": {
    "letterbox": {
      "args": [
        "letterbox"
      ],
      "command": "uvx"
    }
  }
}

This one needs environment variables set before it will start: LETTERBOX_CHANNEL (Channel name to open. Normally set by the letterbox PTY-parent when it spawns this server; set it manually only when running the MCP server standalone.), LETTERBOX_SENDER (This endpoint's identity on the channel — the name the peer agent sees on every message.), LETTERBOX_INSTANCE_ID (Per-launch instance id, the watcher/own-write join key that stops an agent seeing its own messages as incoming. Must be unique per launch.). The author declared them in the registry entry; get the values from the project itself.