3LT Letter Mail MCP server

3LT Letter Mail — MCP Server

Give your AI assistant hands. 3L-Group Technology is a print-and-mail rail: an AI agent calls our MCP tools, and a real physical letter goes out through the U.S. Postal Service. Draft a letter in chat, approve it, and it's in the mail — no printing, no envelopes, no post office run.

🌐 https://3lgrouptechnology.com

Use the hosted service (no setup)

The public MCP endpoint is live:

https://3lgrouptechnology.com/mcp

Transport: streamable HTTP. Authentication: pass your API key as the api_key argument on every tool call. Get an API key at 3lgrouptechnology.com.

Connect from Claude

Claude (claude.ai) supports custom MCP connectors: add a new connector with the server URL above. When the assistant calls a tool, it supplies your lms... API key as the apikey parameter. (The service never sees your Claude account — the key is the only credential.)

Connect from Cursor

Settings → MCP → Add custom MCP server:

{
  "mcpServers": {
    "3lt-letter-mail": {
      "url": "https://3lgrouptechnology.com/mcp"
    }
  }
}

Connect from any MCP client

Any client that speaks streamable HTTP works: point it at https://3lgrouptechnology.com/mcp and provide your API key per tool call.

Tools

There is no tool that mails a letter directly. Every send passes through an approval record: a human tap or a standing Connect authorization.

Pricing

Flat $1.00 service fee per letter, plus postage (USPS First-Class via our print-and-mail provider). One price, no tiers, no volume games. Certified Mail with Electronic Return Receipt is opt-in and costs more — it's never the default.

Example: "Send my 2026 1099s to these 40 people" → your assistant loops draftletter → requestsend → send_status for each recipient. Bulk runs auto-send inside your monthly cap; anything flagged falls back to a one-tap Allow/Deny link. One itemized receipt per send.

Self-hosting

Prefer to run your own rail? The full stack is in this repo.

Quickstart

./quickstart.sh

Creates .venv, installs deps, runs the test suites, and starts the REST API on http://127.0.0.1:8000 (dashboard at /).

With no POSTGRIDAPIKEY set, drafts fail cleanly at address verification — nothing can be mailed. Set a test key to exercise the full flow with simulated sends:

POSTGRID_API_KEY=test_... LMS_ADMIN_TOKEN=pick-a-secret ./quickstart.sh

MCP server (separate terminal):

POSTGRID_API_KEY=test_... .venv/bin/python mcp_server.py
# MCP endpoint: http://127.0.0.1:8001/mcp

What's in the repo

Shortened. The full README is on GitHub.