Shipping Rates & Postage Calculator MCP Server

Ask your AI assistant for live shipping prices. This free Model Context Protocol server gives Claude, ChatGPT, and other MCP clients the same real-time USPS, UPS, and FedEx rates that power this site — no account or API key needed.

Endpoint

https://onlineshippingcalculator.com/api/mcp

Add it to your assistant

Claude (claude.ai)

  1. Open claude.ai/customize/connectors.
  2. Click the + button, then choose Add custom connector.
  3. Name it Shipping Rates (or anything you like).
  4. Paste this URL: https://onlineshippingcalculator.com/api/mcp
  5. Leave the OAuth fields empty (no sign-in needed) and click Add. Then ask Claude a shipping question.

Claude Code

  1. Run: claude mcp add --transport http shipping-rates https://onlineshippingcalculator.com/api/mcp

ChatGPT

  1. Open Settings — under Apps & Connectors, enable Developer mode (Advanced settings) if you haven't already.
  2. Click Create (or Add connector).
  3. Name it Shipping Rates.
  4. Paste this MCP server URL: https://onlineshippingcalculator.com/api/mcp
  5. Set Authentication to None and save.

What you can ask

  • “What's the cheapest way to ship a 5 lb box from 95113 to 10001?”
  • “How many stamps do I need for a 3 oz letter?”
  • “Which stamp denominations should I put on a 4 oz large envelope?”
  • “How much is postage for a postcard?”

Tools

  • get_shipping_rates — live USPS, UPS, and FedEx package rates between US ZIP codes, cheapest first.
  • get_postage_price — current USPS First-Class prices for letters, large envelopes, and postcards, with Forever-stamp counts and exact stamp combinations (the same engine as our envelope calculator).

Both tools are read-only. Rates are live quotes and can change. Package rates are discounted prices for postage purchased online through shipping software — buying at a USPS, UPS, or FedEx store counter costs more. See how the discounts work.

Troubleshooting

  • “Couldn't connect” when adding the connector: double-check the URL is exactly https://onlineshippingcalculator.com/api/mcp and leave all OAuth fields empty — no sign-in is needed.
  • Tool calls suddenly failing: the endpoint is rate-limited to about 10 requests per 10 seconds per network. Wait a few seconds and try again.
  • “Live rate quota reached”: package-rate lookups have a daily limit. Postage and stamp questions still work, and you can always get rates at the calculator.
  • “Available to AI assistants only”: live package rates are served to AI assistants (Claude, ChatGPT, Copilot, Perplexity, Gemini). Scripts and other HTTP clients are pointed to the calculator instead; postage and stamp questions work for every client.
  • Prices look different at the post office: that's expected — quotes are discounted online-postage rates; counter prices are higher.
  • Something else? Contact us with the question you asked and the assistant you used.

Data & privacy

Requests are logged (tool name, request parameters, a truncated IP hash, and client user-agent) to operate and improve the service. No accounts, no cookies, nothing is sold. See our privacy policy.

Support

Questions or problems? Contact us.