MCP Server — Frequently Asked Questions

What it is

What is the api-tester.com MCP server?

It's a hosted Model Context Protocol (MCP) server. Connect it once and your AI coding assistant can drive a cloud headless browser to see a web page — capturing screenshots, running accessibility and performance audits, inspecting the DOM and CSS, and even diagnosing a UI bug from a plain-English description. It's the same team behind the free api-tester.com API testing tool.

How is this different from the free API tester?

The free API tester is for sending and inspecting HTTP requests. The MCP server is for visually reviewing and debugging web UIs from inside your AI assistant. They share one account, one brand and one server — think of the tester as the free everyday tool and the MCP server as the power-up for AI-assisted frontend work.

Which AI assistants does it work with?

Any MCP client that supports SSE transport. It's tested with Claude Code and Cursor, and works with any other SSE-capable MCP client.

What can the AI actually do to my page?

It exposes 16 tools across four categories:

• Capture — page & responsive screenshots.
• Audit — accessibility (WCAG), performance (Core Web Vitals), SEO, page structure, console/network, design tokens, full review.
• Inspect — DOM, computed styles, storage, security headers, memory and detached nodes, unused CSS/JS coverage.
• Diagnose — describe a bug in plain English; get likely causes.

See the full list with parameters in the docs.

Using it

How do I set it up?

1. Grab an API key from the dashboard (email sign-in, no password).
2. Add this block to your MCP client config (Claude Code .mcp.json or Cursor .cursor/mcp.json):

{
  "mcpServers": {
    "api-tester-ui": {
      "url": "https://api-tester.com/mcp/sse",
      "headers": { "x-api-key": "at_your_key_here" }
    }
  }
}

Restart your client and ask it something like: "Take a responsive screenshot of staging.example.com and fix the mobile layout." Full steps for Claude Code and Cursor are in the setup docs.

How do I authenticate?

Send your key as the x-api-key header (preferred). A ?apiKey= query-string fallback exists but may appear in logs, so prefer the header.

Can it test localhost or my private staging site?

No. For security, requests to localhost and private networks are blocked. Only public URLs can be reviewed. To inspect an internal site, expose it temporarily through a public tunnel/domain.

What counts as one "session"?

One MCP/SSE connection = one session. Tool calls inside that connection are unlimited — a full screenshot → audit → fix → re-screenshot loop uses a single session. Sessions reset monthly on your billing date.

Pricing & limits

Is there a free plan?

Yes. The free tier includes 50 sessions per month, 10 requests per minute, and all 16 tools — no credit card required. Paid plans raise the volume and rate limits; see pricing.

I got a 401 / 404 / 429 error — what does it mean?

• 401 — the key is invalid/deactivated, or you've hit your monthly session limit. Check the dashboard.
• 404 — the session closed. Reconnect your MCP client to start a new one.
• 429 — you exceeded your plan's per-minute rate limit. Slow down or upgrade.

Is my page data or API key safe?

Your key is sent only to api-tester.com over HTTPS and is shown once at creation. You can rotate or deactivate it any time from the dashboard. Reviews run against the public URL you provide; private/localhost targets are refused before any loading happens.