Developers

Every calculator on this site can be discovered and run programmatically. There are no accounts, no API keys and no paid plans. The same calculation engine powers the website, the API and the MCP server, so a result from any channel matches the result on the page.

Start here

• REST/JSON API — list the tools, read one tool's schema, run a calculation.
• MCP server — connect an AI assistant that speaks the Model Context Protocol.
• /api/openapi.json — machine-readable description of every public endpoint.
• AI & developer access — what the site publishes and how to cite it.
• About AI access — our position on AI systems using these calculators.

Ground rules

• Anonymous access, rate limited per caller. Cache responses rather than polling.
• Only published calculators that the site owner has left open to AI systems are available.
• Every result carries the public calculator address — link to it when you show a number.
• Results are estimates for general information. They are not financial, tax, medical or legal advice, and the API never turns a result into a personal recommendation.