MCP server for browser-based UI debugging

Give an MCP-compatible AI client a real browser, screenshots, DOM inspection, workflow validation, console capture, API checks, and visual comparison.
_{29 MCP tools · Local, Browserbase, Anchor, or any CDP browser · Node.js 20+}

What VUDA does

VUDA (Visual UI Debug Agent) is a Model Context Protocol server for inspecting and testing web interfaces with Playwright. The MCP server runs locally over standard input/output; its browser can run locally, on Browserbase, on Anchor Browser, or at an existing CDP endpoint. Every tool uses the same selected browser runtime.

• Capture full-page, viewport, element, local-file, and batch screenshots.
• Map interactive elements and inspect rendered DOM and computed styles.
• Execute multi-step UI workflows while preserving browser state.
• Monitor console output and analyze page performance.
• Compare two rendered states and return a visual diff.
• Crawl sitemaps and exercise API endpoints.
• Emulate supported Playwright devices.

Quick start

1. Run VUDA

npx -y visual-ui-debug-agent-mcp

The default local mode needs a Chromium-compatible browser. If one is not already available, install the matching browser once:

npx playwright install chromium

2. Add it to an MCP client

{
  "mcpServers": {
    "vuda": {
      "command": "npx",
      "args": ["-y", "visual-ui-debug-agent-mcp"]
    }
  }
}

Restart the client after changing its MCP configuration. The server writes protocol messages to stdout and diagnostics to its temporary log file.

No provider account is required for local mode.

Docker users can use the same stdio transport:

{
  "mcpServers": {
    "vuda": {
      "command": "docker",
      "args": ["run", "--interactive", "--rm", "ghcr.io/samihalawa/visual-ui-debug-agent-mcp:latest"]
    }
  }
}

To use provider credentials from a file with Docker, add "--env-file", "/absolute/path/to/.env" immediately after "run" in the args array.

3. Try it

Ask your client to:

Use VUDA to inspect https://example.com, capture a screenshot, list the
interactive elements, and report console errors and obvious layout issues.

Tool reference

Analysis and capture

Tool	Purpose
enhanced_page_analyzer	Screenshot, console, performance, and interactive-element analysis
screenshot_url	Capture a URL, viewport, full page, or selected element
batch_screenshot_urls	Capture multiple URLs for side-by-side review
screenshot_local_files	Render and capture local HTML files
dom_inspector	Return element properties, children, and computed styles
visual_comparison	Compare two rendered pages or elements

Workflows, diagnostics, and APIs

Tool	Purpose
ui_workflow_validator	Execute and verify a described user journey
navigation_flow_validator	Validate a sequence of browser actions
console_monitor	Capture browser console messages over a time window
performance_analysis	Collect navigation and page performance metrics
api_endpoint_tester	Exercise multiple HTTP endpoints
sitemap_crawler	Discover and inspect pages from a sitemap
tunnel_helper	Store or retrieve a remote tunnel URL and setup guidance
debug_memory	Keep small debugging notes during one server session

Direct Playwright controls

playwright_navigate, playwright_click, playwright_iframe_click, playwright_fill, playwright_select, playwright_hover, playwright_evaluate, playwright_console_logs, playwright_get_visible_text, playwright_get_visible_html, playwright_go_back, playwright_go_forward, playwright_press_key, playwright_drag, and playwright_screenshot.

Configuration

VUDA reads environment variables normally and automatically loads .env from its working directory. Copy .env.example when running from a source checkout. For an npx installation, either put .env in the MCP process working directory, pass variables in the client configuration, or set DOTENV_CONFIG_PATH to an absolute .env path.

Choose the browser

Mode	Required configuration	Account state
Local (default)	VUDA_BROWSER_PROVIDER=local	VUDA_STORAGE_STATE_PATH, cookie JSON, or a cookie file
Browserbase	VUDA_BROWSER_PROVIDER=browserbase, BROWSERBASE_API_KEY	Reuse BROWSERBASE_CONTEXT_ID or inject cookies
Anchor Browser	VUDA_BROWSER_PROVIDER=anchor, ANCHOR_API_KEY	Use an Anchor profile in VUDA_ANCHOR_SESSION_JSON or inject cookies
Existing browser	VUDA_BROWSER_PROVIDER=cdp, VUDA_CDP_URL	Uses that browser context; cookie injection is optional

Browserbase example:

VUDA_BROWSER_PROVIDER=browserbase
BROWSERBASE_API_KEY=your_api_key
BROWSERBASE_PROJECT_ID=your_project_id
BROWSERBASE_CONTEXT_ID=your_saved_context_id

Anchor Browser example with a persistent authenticated profile:

VUDA_BROWSER_PROVIDER=anchor
ANCHOR_API_KEY=your_api_key
VUDA_ANCHOR_SESSION_JSON={"browser":{"profile":{"name":"vuda","persist":true}}}

All 29 tools keep their existing names and inputs in every mode. Read the MCP resource browser://status to confirm the selected provider, current connection state, session ID, and whether a live view is available. CDP and live-view URLs are never returned.

Import cookies or local state

Cookie injection works with every provider. Supply a Playwright cookie array inline or by file:

VUDA_COOKIES_FILE=/absolute/path/to/cookies.json
# VUDA_COOKIES_JSON=[{"name":"session","value":"...","domain":"example.com","path":"/"}]

For local mode, VUDA_STORAGE_STATE_PATH loads a Playwright storage-state file. Set VUDA_PERSIST_STORAGE_STATE=true to write the updated state back when VUDA exits cleanly. Browserbase Contexts and Anchor profiles are the provider-native choices for state that must survive multiple cloud sessions.

Provider-specific session options remain available without another wrapper or SDK:

• VUDA_BROWSERBASE_SESSION_JSON is merged into Browserbase's create-session request.
• VUDA_ANCHOR_SESSION_JSON is sent as Anchor's create-session request.

Timeouts

All timeout settings are optional:

Variable	Default	Purpose
VUDA_DEFAULT_TIMEOUT	15000	General Playwright timeout in milliseconds
VUDA_NAVIGATION_TIMEOUT	15000	Navigation timeout
VUDA_SELECTOR_TIMEOUT	12000	Selector wait timeout
VUDA_STABILITY_WAIT	5000	Delay after navigation before capture
VUDA_UI_UPDATE_WAIT	1000	Delay for short UI updates
VUDA_PERFORMANCE_THRESHOLD	15000	Slow-page threshold
VUDA_INTERACTION_DELAY	500	Delay between direct interactions

Example:

{
  "mcpServers": {
    "vuda": {
      "command": "npx",
      "args": ["-y", "visual-ui-debug-agent-mcp"],
      "env": {
        "VUDA_NAVIGATION_TIMEOUT": "30000",
        "VUDA_STABILITY_WAIT": "2000"
      }
    }
  }
}

Development

git clone https://github.com/samihalawa/visual-ui-debug-agent-mcp.git
cd visual-ui-debug-agent-mcp
npm ci
npm test

npm test builds the TypeScript server, starts it through the MCP stdio transport, verifies the exact 29-tool inventory, reads a bundled resource, exercises a stateful tool call, and captures a real browser screenshot.

It also validates Browserbase and Anchor session request/cleanup shapes, CDP selection, cookie loading, and the crawler's browser initialization. Provider calls use deterministic mocks in CI; use your own .env for a live cloud session.

Before opening a pull request, also run:

npm audit
npm pack --dry-run

Architecture

VUDA keeps one Playwright control plane across all providers. Local mode creates isolated contexts for page-level analyses; remote modes reuse the provider context so authenticated state survives across tools. VUDA returns screenshots as MCP image content and exposes generated screenshots, browser status, and debugging prompts as MCP resources.

Contributing

Issues and focused pull requests are welcome. See CONTRIBUTING.md for the development workflow and review checklist. Release history is recorded in CHANGELOG.md.

License

ISC © 2023–2026 Sami Halawa and contributors.