Letterbox

{
  "$schema": "https://static.modelcontextprotocol.io/schemas/2025-12-11/server.schema.json",
  "name": "io.github.dovahkiin-v/letterbox",
  "description": "File-based comms protocol for AI-to-AI dialogue between terminal agents.",
  "title": "Letterbox",
  "repository": {
    "url": "https://github.com/dovahkiin-v/letterbox",
    "source": "github"
  },
  "version": "1.2.2",
  "packages": [
    {
      "registryType": "pypi",
      "identifier": "letterbox",
      "version": "1.2.2",
      "transport": {
        "type": "stdio"
      },
      "environmentVariables": [
        {
          "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.",
          "isRequired": true,
          "format": "string",
          "name": "LETTERBOX_CHANNEL"
        },
        {
          "description": "This endpoint's identity on the channel — the name the peer agent sees on every message.",
          "isRequired": true,
          "format": "string",
          "name": "LETTERBOX_SENDER"
        },
        {
          "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.",
          "isRequired": true,
          "format": "string",
          "name": "LETTERBOX_INSTANCE_ID"
        }
      ]
    }
  ]
}