API & MCP

Everything a person can do on Sizewise Big Number Explainer, a program or AI agent can do with the same inputs and get the identical result.

HTTP API

• POST https://sizewisebignumber.usefulweb.app/api/v1/calculate – run Sizewise Big Number Explainer
• GET https://sizewisebignumber.usefulweb.app/api/v1/tool – inputs, output schema, examples
• OpenAPI 3.1: /openapi.json · /openapi.yaml
• Errors: application/problem+json; 422 includes per-field errors.

Sizewise Big Number Explainer

Explains any big number written as digits, words, scientific notation, powers or factorials: exact digits, scientific notation, the short- and long-scale names, how long counting to it takes, how high a stack of banknotes it makes and which famous numbers are close.

Example request

A googol

curl -X POST https://sizewisebignumber.usefulweb.app/api/v1/calculate -H 'content-type: application/json' -d '{"number":"googol"}'

Every result contains

inputs (normalised, defaults applied), summary, result (validated against the published schema), units, assumptions, sources, warnings, computedAt and links.

MCP (Model Context Protocol)

• Streamable HTTP endpoint: https://sizewisebignumber.usefulweb.app/mcp – protocol revisions 2026-07-28 (stateless) and 2025-11-25 / 2025-06-18 / 2025-03-26 (initialize handshake).
• Tools: sizewise_big_number
• Local stdio connector: node src/mcp-stdio.ts --tool=sizewise-big-number

{
  "mcpServers": {
    "sizewise-big-number": { "type": "http", "url": "https://sizewisebignumber.usefulweb.app/mcp" }
  }
}