Setup & documentation

Everything you need to connect Claude Code, Cursor, or any other MCP client to the API Tester UI review server.

1. Get an API key
2. Claude Code setup
3. Cursor setup
4. Authentication options
5. How sessions work
6. Tool reference (all 16)
7. Rate limits
8. Error codes

1. Get an API key

Sign in to the dashboard with your email — we send a magic link, no password needed. A key is created for you automatically on first sign-in and shown once; copy it right away. Keys look like at_… and can be rotated or deactivated from the dashboard at any time.

2. Claude Code

Fastest: one CLI command from your project directory.

claude mcp add --transport sse api-tester-ui https://api-tester.com/mcp/sse \
  --header "x-api-key: at_your_key_here"

Or add it to your project's .mcp.json (checked in, shared with your team):

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

Then ask things like "take a responsive screenshot of staging.example.com and fix anything that looks broken on mobile".

3. Cursor

Add the same block to ~/.cursor/mcp.json (global) or .cursor/mcp.json in your project:

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

Any other MCP client that supports SSE transport works the same way — point it at https://api-tester.com/mcp/sse with your key.

4. Authentication options

Two ways to present your key — the header is preferred:

x-api-key: at_your_key_here

If your client can't set headers, append the key as a query parameter instead (be aware it may end up in logs):

https://api-tester.com/mcp/sse?apiKey=at_your_key_here

5. How sessions work

One SSE connection = one session credit. When your MCP client connects, one session is deducted from your monthly quota. Within that connection your assistant can make unlimited tool calls — a full review loop (screenshot, audit, fix, re-screenshot) costs a single session. Sessions reset monthly on your billing date; usage is visible on the dashboard.

6. Tool reference

All 16 tools take a public url. Requests to localhost and private networks are blocked, same as the main API tester.

Tool	What it does	Key parameters
Capture
`take_screenshot`	Screenshots a page at a chosen viewport — full page or a single element.	`url`, `viewport`, `fullPage`, `selector`, `waitForSelector`, `delay`
`take_responsive_screenshots`	Screenshots at mobile (375), tablet (768), desktop (1440) and wide (1920) in one call.	`url`, `fullPage`, `delay`
Audit
`audit_accessibility`	WCAG accessibility audit with violations and the selectors that trigger them.	`url`, `standards`, `includeSelectors`
`get_performance_metrics`	Core Web Vitals and load timings for the page.	`url`
`analyze_page_structure`	Heading hierarchy, landmarks and semantic outline.	`url`
`analyze_seo`	Title, meta description, canonical, Open Graph and robots checks.	`url`
`get_console_and_network`	Console messages plus network requests and failures during load.	`url`, `captureNetwork`
`extract_design_tokens`	Colors, font stacks and spacing values actually used on the page.	`url`
`full_ui_review`	Runs the whole audit suite and returns one combined report.	`url`, `viewport`, `depth` (standard \| deep)
Inspect
`inspect_element`	DOM inspection of a selector: attributes, children, parents, event listeners.	`url`, `selector`, `includeChildren`, `childDepth`, `includeParents`, `includeEventListeners`
`inspect_styles`	Computed and matched CSS for a selector, including inherited and overridden rules.	`url`, `selector`, `pseudoElement`, `showInherited`, `showOverridden`
`analyze_storage`	Cookies, localStorage, sessionStorage, IndexedDB, Cache API and service workers.	`url`, `includeCookies`, `includeLocalStorage`, `includeIndexedDB`, …
`analyze_security`	Security headers, mixed content and TLS certificate checks.	`url`, `checkHeaders`, `checkMixedContent`, `checkCertificate`
`profile_memory`	JS heap profile and detached DOM node detection.	`url`, `checkDetachedNodes`, `waitBeforeProfile`
`analyze_coverage`	Unused CSS and JS bytes per file — find dead weight.	`url`, `includeCSS`, `includeJS`
Diagnose
`diagnose_issue`	Describe a UI problem in plain English; it investigates and reports likely causes.	`url`, `issue`, `selector`, `category`

7. Rate limits

Plan	Sessions / month	Requests / minute
Free	50	10
Starter	500	30
Pro	5,000	100
Enterprise	Custom	Custom

Need more? See pricing or email hello@api-tester.com.

8. Error codes

Status	Meaning	What to do
`401`	Invalid or deactivated API key, or your monthly session limit is reached.	Check the key in your config, or check usage on the dashboard and upgrade if needed.
`404`	Session not found — the SSE connection it belonged to has closed.	Reconnect your MCP client to start a fresh session.
`429`	Rate limit exceeded for your plan.	Slow down or upgrade for a higher per-minute limit.