Letterbox MCP server

by dovahkiin-v·io.github.dovahkiin-v/letterbox·v1.2.2

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

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If you have run it, two minutes of your experience saves the next person an afternoon.

No tool declarations could be read from the package source. They show once the server is installed.

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claude mcp add letterbox -- uvx letterbox

Is Letterbox MCP server safe?: Not known yet: the safety scan has not run. New listings are scanned within a few days.
How do I install Letterbox?: It runs on your machine. Copy the Claude Code, Claude Desktop or Cursor config from the install section.
Does Letterbox need an API key?: No secret keys are declared. It reads 3 settings from the environment.
Is Letterbox maintained?: The latest release is v1.2.2.

Local package. It runs on your machine, not through the gateway.

LETTERBOX_CHANNELChannel 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_SENDERThis endpoint's identity on the channel — the name the peer agent sees on every message.
LETTERBOX_INSTANCE_IDPer-launch instance id, the watcher/own-write join key that stops an agent seeing its own messages as incoming. Must be unique per launch.

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