Letterbox MCP Server: Install & Setup

Install Letterbox in Claude Code

Claude Code

claude mcp add letterbox -e LETTERBOX_CHANNEL=... -e LETTERBOX_SENDER=... -e LETTERBOX_INSTANCE_ID=... -- uvx letterbox

mcp.json (Claude Desktop, Cursor, VS Code, Windsurf)

{
  "mcpServers": {
    "letterbox": {
      "command": "uvx",
      "args": [
        "letterbox"
      ],
      "env": {
        "LETTERBOX_CHANNEL": "...",
        "LETTERBOX_SENDER": "...",
        "LETTERBOX_INSTANCE_ID": "..."
      }
    }
  }
}

Replace each ... with your own value.

Frequently asked questions

What does the Letterbox MCP server do?

File-based comms protocol for AI-to-AI dialogue between terminal agents.

Is the Letterbox MCP server free?

Yes, most likely. Open source and no paid account or API key is mentioned in the listing. Check the provider for current pricing.

Does Letterbox run locally or remotely?

Local. Runs on your machine (stdio). You install it with npx, uvx, Docker or from source.

How do I add Letterbox to Claude Code?

Run: claude mcp add letterbox -e LETTERBOX_CHANNEL=... -e LETTERBOX_SENDER=... -e LETTERBOX_INSTANCE_ID=... -- uvx letterbox

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