Automated Thank-You Notes with AI

The pattern

The agent watches for an event — a closed deal, a positive support resolution, a meeting that mattered. It fetches what it needs to know, drafts a short note in your voice, and calls send_letter. The recipient holds something physical, sent by software.

A minimal setup

Wire Mailsnail in via /setup.
Give the agent access to whatever data source decides who gets a note (CRM, calendar, support tool).
Provide a short voice/style guide and a few example notes for in-context learning.
Run on a schedule, or trigger from a webhook.

Prompt pattern

You are a thoughtful assistant who writes brief, hand-written-feeling thank-you notes (4-6 sentences). When you decide to send one, call send_letter. Don't send more than one note per recipient per 30 days. Skip recipients who don't have a complete mailing address.

Quality controls

Always pass from so recipients know who sent it.
Keep a log of who got a note and the receipt_token each send returns, and check it before sending again.
Let the agent call preview_letter freely (it charges nothing) and keep send_letter behind an approval step until you trust the drafts.
Run a moderation step on the draft before the tool call.

Beyond thank-yous

The same shape works for condolence cards, congratulations on a promotion, follow-ups after a great first call, and similar one-shot, decided-by-context pieces of mail.

Wire Mailsnail into your agent

Add one URL and sign in. Nothing to install and no API key. In Claude Code:

Claude Code

claude mcp add -t http mailsnail https://api.mailsnail.dev/mcp

Then run /mcp and choose Authenticate. In Claude Desktop or ChatGPT, add https://api.mailsnail.dev/mcp as a custom connector. Cursor and other JSON-config clients take:

mcp.json

{
  "mcpServers": {
    "mailsnail": {
      "url": "https://api.mailsnail.dev/mcp"
    }
  }
}

A one-page letter is from $1.21, and preview_letter shows the proof and exact price before anything is charged. Setup for every app →