> ## Documentation Index
> Fetch the complete documentation index at: https://iotools.cloud/docs/llms.txt
> Use this file to discover all available pages before exploring further.

# IOTools.cloud API

> Call 800+ developer tools over one REST endpoint, or from any MCP client

Most tools on [IOTools.cloud](https://iotools.cloud) are also an API endpoint and an MCP tool — **800+ of them**. One key, one credit balance, both surfaces.

<CardGroup cols={2}>
  <Card title="Quick start" icon="rocket" href="/docs/quick-start">
    First call in about two minutes
  </Card>

  <Card title="API reference" icon="code" href="/docs/api-reference">
    Every endpoint, with a live playground
  </Card>

  <Card title="Use it from an agent" icon="robot" href="/docs/mcp/overview">
    Claude, Cursor, Windsurf — one config block
  </Card>

  <Card title="Credits" icon="coins" href="/docs/concepts/credits">
    What a call costs
  </Card>
</CardGroup>

## One call

```bash theme={"system"}
curl -X POST https://api.iotools.cloud/v1/tool/case-converter \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{ "ioInputString": "hello world", "ioCase": "uppercase" }'
```

```json theme={"system"}
{
  "request_id": "e4042b29-…",
  "tool": "case-converter",
  "tool_version": "1",
  "outputs": { "ioOutputString": "HELLO WORLD" },
  "credits_used": 1,
  "credits_remaining": 999
}
```

## Two things to know first

**Using a tool in your browser is free and unlimited. Calling it from code costs credits.** Every tool call over the API or MCP costs credits, including tools that cost nothing on the website — a per-plan minimum, or the tool's own weight if that is higher. Reading the catalog costs nothing. See [Credits](/docs/concepts/credits).

**Not every tool has an API.** 800+ tools on the site do. The rest run entirely in your browser — camera capture, some PDF and image editing — and have no server-side equivalent to call. Calling one returns `tool_not_allowed`; see [Errors](/docs/concepts/errors).

## What you get

<CardGroup cols={2}>
  <Card title="800+ endpoints" icon="wrench">
    Formatters, converters, generators, calculators, encoders — the same code that runs on the site.
  </Card>

  <Card title="One schema everywhere" icon="arrows-to-circle">
    The OpenAPI document, the MCP `inputSchema` and the runtime validator come from one source, so they cannot disagree.
  </Card>

  <Card title="Failed calls are free" icon="rotate-left">
    Credits are charged on entry and refunded on any 4xx or 5xx.
  </Card>

  <Card title="RFC 9457 errors" icon="triangle-exclamation">
    Every failure is a problem document with a stable `code` to branch on.
  </Card>
</CardGroup>