Koskamo

Letterbox MCP

A file-based communication protocol enabling real-time messaging between terminal AI agents like Claude Code, Gemini CLI, and Antigravity. It allows agents to collaborate hands-free by passing JSON message files through a shared directory using atomic renames, eliminating the need for a central server or network connection.

Package and access

Local package with source-attributed installation metadata. Koskamo does not execute packages during review.

Letterbox MCP logo, by dovahkiin-vCommunity listingLocal stdioSource reviewed; not executedPublished by dovahkiin-v
Vendor documentation

What you can do with it

  • Enable real-time collaboration between Claude Code and Gemini CLI agents
  • Allow two terminal AI agents to hold a direct conversation without manual copy-pasting
  • Support automated planning loops where one agent drafts and another reviews

Source and maintenance

Community listingRegistry 1.2.2MIT
mcp-registry: io.github.dovahkiin-v/letterbox@1.2.2Source repository
Last repository push
Latest release
v1.2.0
Maintenance checked

Packages and installation

Source-provided package data. Koskamo has not executed or live-probed this package.

letterbox 1.2.2

pypi
letterbox package definition
{
  "version": "1.2.2",
  "transport": "stdio",
  "identifier": "letterbox",
  "registryType": "pypi",
  "environmentVariables": [
    {
      "name": "LETTERBOX_CHANNEL",
      "format": "string",
      "isRequired": true,
      "description": "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."
    },
    {
      "name": "LETTERBOX_SENDER",
      "format": "string",
      "isRequired": true,
      "description": "This endpoint's identity on the channel — the name the peer agent sees on every message."
    },
    {
      "name": "LETTERBOX_INSTANCE_ID",
      "format": "string",
      "isRequired": true,
      "description": "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."
    }
  ]
}

Tools

Reported by the attributed source; not independently observed by Koskamo.

No tool definitions available.

Maintenance history

Public check and source-refresh events. Editorial and ownership records remain private.

  • · repository · passed · metadata changed · updated
  • · backfill · recorded · Pre-expansion baseline; unobserved rich metadata remains unknown

Connect from your client

Each snippet configures the same source-provided package; replace placeholders before use.

This server is operated by the named third party. Listing and endpoint checks are not an endorsement or a security audit. Review the operator's permissions, terms, and data handling before connecting. How listings are checked and corrected.

Cursor

Merge this local stdio configuration, replace every placeholder environment value, and restart Cursor. Koskamo has not executed this package.
Cursor configuration
{
  "mcpServers": {
    "letterbox-mcp": {
      "command": "uvx",
      "args": [
        "letterbox==1.2.2"
      ],
      "env": {
        "LETTERBOX_CHANNEL": "<YOUR_LETTERBOX_CHANNEL>",
        "LETTERBOX_SENDER": "<YOUR_LETTERBOX_SENDER>",
        "LETTERBOX_INSTANCE_ID": "<YOUR_LETTERBOX_INSTANCE_ID>"
      }
    }
  }
}

Cline

Merge this local stdio configuration, replace every placeholder environment value, and restart Cline. Koskamo has not executed this package.
Cline configuration
{
  "mcpServers": {
    "letterbox-mcp": {
      "command": "uvx",
      "args": [
        "letterbox==1.2.2"
      ],
      "env": {
        "LETTERBOX_CHANNEL": "<YOUR_LETTERBOX_CHANNEL>",
        "LETTERBOX_SENDER": "<YOUR_LETTERBOX_SENDER>",
        "LETTERBOX_INSTANCE_ID": "<YOUR_LETTERBOX_INSTANCE_ID>"
      }
    }
  }
}

VS Code

Merge this local stdio configuration, replace every placeholder environment value, and restart VS Code. Koskamo has not executed this package.
VS Code configuration
{
  "servers": {
    "letterbox-mcp": {
      "type": "stdio",
      "command": "uvx",
      "args": [
        "letterbox==1.2.2"
      ],
      "env": {
        "LETTERBOX_CHANNEL": "<YOUR_LETTERBOX_CHANNEL>",
        "LETTERBOX_SENDER": "<YOUR_LETTERBOX_SENDER>",
        "LETTERBOX_INSTANCE_ID": "<YOUR_LETTERBOX_INSTANCE_ID>"
      }
    }
  }
}

Claude Desktop

Merge this local stdio configuration, replace every placeholder environment value, and restart Claude Desktop. Koskamo has not executed this package.
Claude Desktop configuration
{
  "mcpServers": {
    "letterbox-mcp": {
      "command": "uvx",
      "args": [
        "letterbox==1.2.2"
      ],
      "env": {
        "LETTERBOX_CHANNEL": "<YOUR_LETTERBOX_CHANNEL>",
        "LETTERBOX_SENDER": "<YOUR_LETTERBOX_SENDER>",
        "LETTERBOX_INSTANCE_ID": "<YOUR_LETTERBOX_INSTANCE_ID>"
      }
    }
  }
}

Let your agent find its tools

Find servers like Letterbox MCP from your agent. Add Koskamo once to search the index for endpoints, access requirements, and client setup. Public discovery needs no key.

Connect Koskamo Explore workflows
See all 7,816