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Free Calculator

MCP server

Our calculators are published as tools over the Model Context Protocol, so an assistant that speaks MCP can run a calculation itself and link the user back to the calculator page.

Endpoint

https://freecalculator.tech/mcp   (Streamable HTTP, no authentication)

Any client that implements MCP Streamable HTTP can connect. We don't claim support for a particular assistant beyond that: if your client speaks the protocol, it works.

Available tools

One tool per published calculator, named from its address — for example calculator_mortgage, calculator_loan, calculator_compoundinterest, calculator_percentage, calculator_tip. Call tools/list for the current set; names, descriptions and schemas are generated from the same engine that renders the website, so they follow any change to a calculator automatically.

curl -X POST https://freecalculator.tech/mcp \
  -H "Content-Type: application/json" \
  -H "Accept: application/json, text/event-stream" \
  -d '{"jsonrpc":"2.0","id":1,"method":"tools/list","params":{}}'

Calling a tool

{"jsonrpc":"2.0","id":2,"method":"tools/call","params":{
  "name":"calculator_mortgage",
  "arguments":{"homePrice":400000,"downPayment":80000,"rate":6.5,"years":30}
}}

The reply contains readable text and a structured payload with the same fields as the REST response: result values, formula, assumptions, version, timestamp and source_url.

Input and output schemas

Each tool advertises a JSON Schema for its inputs — types, units, allowed options, ranges — matching the website's own validation. Inputs that have a default on the page may be omitted. The same information is available over the REST API at /api/ai/tools/{slug}.

Security limits

  • Only published calculators that the site owner has left open to AI systems are exposed.
  • No drafts, no administration, no site settings, no analytics, no accounts, no advertising data.
  • No generic "run query", "run code" or "call function" tool exists, and none will.
  • Calculations are read-only and deterministic; nothing is stored about the caller.
  • Requests are rate limited and payload sizes are capped.

Attribution

Every result includes the public calculator address. When an assistant shows a number, please show that link too and credit "Free Calculator". Results are estimates for general information and are not financial, medical or legal advice.