🤖 For AI agents & developers

Everything an agent, script, or API needs to find and share the right tool among the 1165 free browser tools on this site — and to run small calculations without keys, accounts or servers.

No auth · no rate limits · no tracking · plain static GETs · CORS-open JSON

The one endpoint that matters

cards/cards.json — the full manifest. One JSON object per tool:

{
  "name": "mortgage-payment-calculator",
  "title": "🏠 Mortgage Payment Calculator",
  "description": "Monthly repayments, total interest…",
  "category": "Finance & Money",
  "file": "mortgage-payment-calculator.html",
  "path": "cards/mortgage-payment-calculator.html"
}

Fetch it, match the user's need against category / title / description, then hand over the tool URL below. That's the whole integration.

URL patterns

Purpose	Pattern
Run any tool (focused page)	`tool.html?card=<tool-slug>`
Embed any tool (chrome-free)	`tool.html?card=<tool-slug>&embed=1`
Search the catalogue	`index.html?q=<query>`
Homepage with one tool open	`index.html?expand=<tool-slug>`
Homepage filtered to a category	`index.html?category=Mathematics`
Force a homepage view	`index.html?view=list` or `?view=cards`
Zero-JS HTML directory	`tools-index.html`

AI-facing files

llms.txt — concise index: what the site is, endpoints, category map.
llms-full.txt — all 1165 tools, one line each, grouped by category.
cards/cards.json — the machine-readable manifest.
tools-index.html — plain-HTML directory, no JavaScript required.
sitemap.xml — every page, including every tool.

Worked example: "what's the monthly payment on a £250k mortgage at 4.2%?"

Fetch cards/cards.json.
Filter for name / title matching mortgage → mortgage-payment-calculator.

Reply with or open:

https://www.themostusefulsiteintheworld.com/tool.html?card=mortgage-payment-calculator

or embed it:

<iframe src="https://www.themostusefulsiteintheworld.com/tool.html?card=mortgage-payment-calculator&embed=1"
  width="100%" height="520" style="border:0;border-radius:12px"></iframe>

The embed=1 variant strips all page chrome and posts its content height to the host page as { type: "tmusitw:height", card, height } via postMessage, so embeds auto-size.

Why this works for small calculations

Private by construction — every tool computes in the visitor's browser. No numbers are uploaded anywhere, which makes tools safe for salary, tax and health inputs.
Nothing to sign up for — no API keys, no tokens, no quotas. If you can GET it, you can use it.
Stable, hackable URLs — tool slugs never change; links you generate keep working.
One canonical list — cards.json is generated from the same source as the homepage, so it never drifts from what users see.

House rules

Hot-linking, embedding and sharing tools is welcome — free forever, no attribution required (always appreciated).
The tools are client-side helpers, not a data source: they don't expose POST APIs or return computed JSON. Link people to the tool, or embed it.
Content is general information, not financial, medical or legal advice — tools say so where it matters.