Postage Stamp Price MCP

postage-stamp-price-mcp

How much is a stamp, for AI assistants. Ask what a Forever stamp costs, what it takes to mail 40 square holiday cards, or what a letter to Germany costs, and get the current USPS price with its effective date.

This is a Model Context Protocol (MCP) server. It reads USPS Notice 123, the official retail price list on Postal Explorer, at call time. Prices are matched by the USPS SKU on each price cell. It needs no API key.

Tools

Tool	What it returns
get_stamp_price	The current Forever stamp price (1 oz First-Class Mail letter), 2, 3 and 3.5 oz prices, metered prices, postcard, 1 oz large envelope, nonmachinable surcharge and the 1 oz international letter (Global Forever) price, with the effective date.
calculate_letter_postage	Postage for a letter, postcard or large envelope by weight, to the US, Canada, Mexico or another country, with the nonmachinable surcharge, a total for a quantity and the number of Forever stamps per piece.
get_flat_rate_prices	Retail Priority Mail and Priority Mail Express flat rate envelope and box prices.

Every result has structured JSON, a one-paragraph summary, as_of, source and more (a page on mcpstamp.com).

What it knows that your model does not

• The price in force today. USPS changes prices once or twice a year, so a remembered stamp price is often wrong.
• The effective date of the price list, so the answer can say when the price started.
• Surcharges and weight steps, so "two stamps or one?" has an exact answer.

Install

Hosted (Claude.ai custom connector, ChatGPT developer mode)

Paste this URL. No token, no sign-up. It works now.

https://postage-stamp-price-mcp.lipmichal.workers.dev/mcp

Claude Code

claude mcp add --transport http stamp-price https://postage-stamp-price-mcp.lipmichal.workers.dev/mcp

Claude Desktop

Claude Desktop adds remote servers under Settings, Connectors, Add custom connector. Paste the URL above.

Cursor

Add to ~/.cursor/mcp.json:

{
  "mcpServers": {
    "stamp-price": { "url": "https://postage-stamp-price-mcp.lipmichal.workers.dev/mcp" }
  }
}

VS Code

Add to .vscode/mcp.json:

{
  "servers": {
    "stamp-price": { "type": "http", "url": "https://postage-stamp-price-mcp.lipmichal.workers.dev/mcp" }
  }
}

Local stdio (after npm release)

The npm package is not published yet. After it is, run it locally with Node 20 or newer:

claude mcp add stamp-price -- npx -y postage-stamp-price-mcp

Example prompts

• "How much is a stamp right now?"
• "How much postage do I need for 40 square Christmas cards that weigh 1.2 oz?"
• "How much does it cost to mail a letter to Germany?"
• "How much is a medium flat rate box?"
• "How much is a postcard stamp?"

Data sources

Full list with fetch dates in DATA_SOURCES.md.

• USPS Notice 123 Price List, read at call time.

Limitations

• Retail prices at the Post Office. Commercial, metered and Click-N-Ship prices can be lower; metered letter prices are included.
• Packages (Ground Advantage, Priority Mail by zone) are not covered beyond flat rate. Use https://postcalc.usps.com/ for those.
• International large envelopes are not covered yet.
• The hosted server caches the price list for up to 6 hours.

More

More MCP servers that answer questions your assistant cannot answer alone are on mcpstamp.com.

Part of the Zovo MCP collection: https://mcp.zovo.one

Built by theluckystrike.

Development

npm install
npm test                              # builds, then runs the fixture tests and an offline stdio test
node scripts/stdio-transcript.mjs     # live stdio round trip, writes .live/stdio-transcript.jsonl

License

MIT