Pixelcheck

What pixelcheck MCP server does

The pixelcheck MCP server connects an MCP client to rendered web pages through a locally running Chromium browser. It gives an agent ways to inspect a page, perform browser actions, retrieve structured content, and evaluate one or two URLs against defined criteria.

The see tool captures a single view and can return a DOM summary, screenshot, console errors, and an optional natural-language note. Omitting the goal avoids LLM cost for that operation. act runs sequences such as clicks, form fills, scrolling, screenshots, natural-language actions, and vision notes, then reports step results and the final page state.

For data collection, extract accepts a JSON Schema and returns data shaped to that schema, along with page diagnostics and a screenshot. judge scores a URL against a custom rubric, returning criterion scores from 0 to 10 and findings with severity and on-screen locations. compare applies the same rubric to two URLs; its default double-blind mode evaluates each independently before synthesizing the result, while fast uses one vision call.

How it works

The server exposes the browser primitives and additional workflow tools over MCP. audit_url runs the full audit pipeline for one URL and produces JSON and HTML reporting. explore_url performs an autonomous run from a free-form goal without requiring scenario YAML. The audit preset can also combine personas and scenarios for broader product reviews.

Project discovery tools include list_personas and list_scenarios. list_capabilities reports the available tools, their cost and cacheability information, side effects, dependencies, public environment variables, and live result-cache state. calibrate_critic checks the critic against labeled fixtures and returns pass/fail information with agreement metrics. get_last_report reads the latest audit summary from the local history database.

Setup and configuration

Install the package globally with npm, then run the diagnostic command before starting the MCP process:

npm install -g pixelcheck
pixelcheck doctor
pixelcheck-mcp

The browser binary is installed during package installation. The documented MCP configuration uses the pixelcheck-mcp command with stdio transport. A typical client entry passes ANTHROPIC_API_KEY in the server environment:

{
  "mcpServers": {
    "pixelcheck": {
      "command": "pixelcheck-mcp",
      "env": { "ANTHROPIC_API_KEY": "sk-ant-..." }
    }
  }
}

Restart the MCP client after adding the configuration. The pixelcheck MCP server is documented for Claude Desktop, Cursor, Cline, Continue, Zed, and Claude Code.

Limitations and notes

The pixelcheck MCP server runs locally and does not use remote storage or telemetry according to the project documentation. Its stated outbound destination is the LLM provider used for agent or vision-critic work. Vision-based scoring sends audit data to Anthropic after opt-in on the first run, so teams should account for that data flow before using critic or audit features.

The repository documents Claude support today. OpenAI, Gemini, and Ollama-local provider support is described as a future roadmap item rather than a current capability. The audit preset complements traditional end-to-end tests; it is presented as a product-experience review layer, not a replacement for functional E2E coverage.