MCP server · for AI agents

The way AI agents send physical mail.

Mailsnail is an MCP server that lets Claude, Cursor, Codex, and any agent send real letters and postcards. No signup, no humans in the loop — pay per piece via Stripe Link.

Wire it into your agentSee how it works
claude_desktop_config.json
{
  "mcpServers": {
    "mailsnail": {
      "command": "npx",
      "args": [
        "-y",
        "physical-mail-mcp"
      ],
      "env": {
        "MAIL_PROVIDER": "managed",
        "MAIL_API_BASE_URL": "https://api.mailsnail.dev"
      }
    }
  }
}

From tool call to mailbox in three steps

No printers, no postage, no envelope-licking. No signup.

1

Your agent calls send_letter

From Claude Code, Cursor, an autonomous loop, or anything that speaks MCP. Pass body text and a recipient address.

2

It pays with Stripe Link

The agent mints a Shared Payment Token (SPT) from a Link wallet — pay-per-piece, no account on our side.

3

It arrives in their mailbox

We render, print, fold, stamp, and hand to USPS the same business day. The recipient holds something physical — sent by software.

Tools your agent gets

Six tools, all well-typed. Discoverable through llms.txt and /openapi.json.

send_letter

Mail a physical letter to any US address. Pass `body_text` (we render the PDF) or `file_url` (your own PDF). `extra_service: "certified"` for certified mail with tracking.

send_postcard

Send a postcard with a custom front and back. 4x6, 6x9, or 6x11.

verify_address

USPS CASS validation. Free. Run this before sending so you stop paying for return-to-sender mail.

get_letter

Look up status for any piece your agent has sent: queued, in_production, in_transit, delivered.

list_letters

Page through everything the agent has sent on this account.

cancel_letter

Cancel a letter before it enters production. Cancellation windows are short.

What agents actually mail

Customer thank-you notes

Your support agent autonomously drops a handwritten-style note in the mail after a positive interaction.

Legal notices & compliance mail

Agents handle preliminary notices, lien letters, and regulated correspondence with audit trails.

Personal post from your AI

Birthday cards, condolence letters, RSVP replies — the things humans should send but never get around to.

Cold outreach with proof

Targeted physical mail to the 50 people who actually matter, written and dispatched by an agent.

Pay per piece. No subscription.

Agent mints an SPT for the quoted amount, we charge once, mail goes out. If mailing fails, the charge is auto-refunded.

$1.50
First-class letter
$9.00
Certified letter
$1.00
Postcard (4x6)

Built to be discovered by agents

If a model is reading this site cold, it can self-onboard in under a minute.

/llms.txt

Tight, machine-readable summary of what this server does and how to call it.

/llms-full.txt

Full docs in one file: tool schemas, examples, MCP config, and pricing.

/openapi.json

OpenAPI 3.1 spec for direct HTTP integration if MCP isn't available.

/setup

Copy-pasteable wiring for Claude Code, Cursor, Codex, and anything else that speaks MCP.

Give your agent a return address.

Two minutes from here to a postmarked letter, sent by your agent.

Get startedRead the full docs