MCP server · for AI agents

The way AI agents send physical mail.

Mailsnail lets Claude, Cursor, and any MCP client send real letters and postcards. Add one server, sign in from your client, and your agent can put paper in a mailbox.

Get started See how it works

Claude Code

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

Then run /mcp and sign in. Claude Desktop, Cursor, and self-hosted setup →

From tool call to mailbox in four steps

No printers, no postage, no envelope-licking. No API keys to provision.

Add the server

One line in Claude Code, or paste the URL into Claude Desktop or Cursor. Nothing to install.

Sign in from your client

Your client hits the server, gets pointed at our sign-in page, and registers itself. You approve it in the browser once.

Fund a balance

The first send hands back a Stripe link. Add a card, pick an opening balance, retry. Stripe holds the card — we never see the number.

It arrives in their mailbox

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

Get started

Tools your agent gets

Well-typed, and discoverable through llms.txt and /openapi.json.

preview_letter

Generate a proof PDF and the exact price WITHOUT charging or mailing. The recommended first step: preview, show the user, then send_letter with the returned draft_id.

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 from a PDF you host, with a custom front and back.

verify_address

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

get_balance

Balance, saved card, and auto-reload settings. Free. Lets an agent check it can afford the job before it starts.

get_letter

Look up status for any piece: queued, in_production, in_transit, delivered.

Plus add_payment_method and top_up for billing. Running it yourself against your own Click2Mail or Lob account adds list_letters and cancel_letter — see self-hosted setup.

What agents actually mail

Customer thank-you notes

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

Legal notices & compliance mail

Preliminary notices, lien letters, and regulated correspondence that legally have to go on paper — with certified tracking and a signed return receipt when you need proof of delivery.

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.

Mail is drawn from a prepaid balance, so one card charge covers many pieces instead of paying a processing fee on every $1.50 letter.

$1.50

First-class letter

$9.75

Certified letter

$17.00

Certified + return receipt

$1.00

Postcard (4x6)

preview_letter quotes the exact price before anything is charged. Unspent balance is refundable — how billing works.

Built to be used 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, Claude Desktop, Cursor, Codex, and anything else that speaks MCP.

Give your agent a return address.

Add the server, sign in, and your agent can mail its first letter.

Get started Read the full docs