Send Physical Mail from Claude Code

Why this is interesting

Claude Code already runs your terminal: it can edit files, hit APIs, run tests, deploy. The one thing it couldn't do until recently was reach the physical world. Mailsnail closes that gap. Once you've registered the MCP server, the agent can call send_letter and a real, postmarked envelope shows up at any US address.

One-line setup

From inside any Claude Code project:

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

Then run /mcp, select mailsnail, and choose Authenticate. Your browser opens our sign-in page; approve it and the tools appear on the next turn. Nothing to install and no API key to paste. Adding the server doesn't open the browser by itself, so if nothing happened after the command, you just haven't started sign-in yet.

After that, the agent has verify_address, preview_letter, send_letter, get_letter, and cancel_letter available, plus get_balance and add_payment_method for funding.

A worked example

In a Claude Code session:

Send a thank-you note to my landlord at 1 Main St, Brooklyn NY 11201, signed from "Resident in 4B," thanking her for the quick repair this morning.

The agent calls verify_address, then preview_letter, which returns a proof and the exact price (from $1.21 for a one-page letter from a balance) with nothing charged. On your go-ahead it calls send_letter and gets back a receipt token for tracking. If your balance is empty, the first send hands back two Stripe links: one to pay for just that letter ($1.51), one to add funds. Pay, and the agent retries.

What to do next

• Walk through the full setup page for screenshots and edge cases.
• Read the complete tool reference if you want to give the agent richer instructions.
• Look at the OpenAPI spec if you'd rather call the HTTP API directly.

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

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