Letterbox MCP Server

Letterbox is an MCP integration. File-based comms protocol for AI-to-AI dialogue between terminal agents.

Packages and local setup

The published pypi package is letterbox, version 1.2.2. Its declared MCP transport is stdio.

The package declares LETTERBOX_CHANNEL (required): 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 (required): This endpoint's identity on the channel — the name the peer agent sees on every message.; LETTERBOX_INSTANCE_ID (required): 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..

Before connecting

Check the maintainer’s instructions for account access, authentication and the supported client configuration. Once connected, inspect the tools your client receives and try a small task that matches the server’s stated purpose. The registry description does not include a verified, complete tool list.

Project and source

View the publisher’s registry entry · Project repository. This profile uses version 1.2.2 from the registry. Registration identifies the publisher namespace; it does not establish that this is a first-party integration for every service it connects.

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