cowork-qa-mcp

demo

A Model Context Protocol server that gives an LLM a real Chromium browser, records every action it takes toward a stated goal, and hands back a structured trace so the LLM (or a second LLM) can decide whether the goal was actually achieved.

Built on Playwright. Five tools, one binary, no cloud dependency.

Why

Most browser-tool MCP servers are stateless — the LLM clicks, gets HTML back, repeats. There's no record of what happened, no way to grade the run after the fact, and no goal context.

cowork-qa-mcp flips that:

Every session starts with a goal in plain English.
Every action (goto, click, fill, press, eval) is recorded with timestamps, the URL after, and the page's aria-snapshot.
When the session ends, a JSON trace is persisted to disk and exposed via a single qa_get_trace call.

The orchestrating LLM can then reason over the trace ("did this run actually fulfill the goal, or did it click the wrong button?") instead of trusting the run-time chatter.

Tools

Tool	What it does
`session_start`	Open a fresh tab, optional starting URL, return a session id
`session_act`	Run one of: `goto`, `click`, `fill`, `press`, `eval`. Records the step.
`session_observe`	Return current URL + full aria-snapshot of the page
`session_end`	Close the tab, persist the trace to disk, return the file path
`qa_get_trace`	Return the goal, every step, final URL, and final aria-snapshot — formatted for an LLM to read

Install

Requires Node 20+. The package is on npm — no clone needed.

bash

# Try it once, no install
npx cowork-qa-mcp

# Or install globally
npm install -g cowork-qa-mcp

The first install pulls Chromium via Playwright's postinstall (~150 MB).

Wire into your MCP-compatible client

Claude Code

Terminal

claude mcp add cowork-qa --scope user -- npx -y cowork-qa-mcp

To watch the browser instead of running headless:

Terminal

claude mcp add cowork-qa --scope user \
  -e COWORK_QA_HEADED=1 \
  -- npx -y cowork-qa-mcp

Verify with /mcp inside a fresh claude session — you should see cowork-qa ✓ connected and 5 tools.

Claude Desktop

Add to ~/Library/Application Support/Claude/claude_desktop_config.json (macOS) or %APPDATA%\Claude\claude_desktop_config.json (Windows):

config.json

{
  "mcpServers": {
    "cowork-qa": {
      "command": "npx",
      "args": ["-y", "cowork-qa-mcp"]
    }
  }
}

Cursor / Windsurf / other MCP clients

Any client that speaks the MCP stdio transport works. Point its server config at npx -y cowork-qa-mcp.

From source (for development)

bash

git clone https://github.com/inSideos-designs/cowork-qa-mcp.git
cd cowork-qa-mcp
npm install
npm run build
node dist/server.js   # stdio server, expects an MCP client

MCP Registry

This server is also published on the official MCP Server Registry as io.github.inSideos-designs/cowork-qa — clients that auto-discover from the registry will find it without any manual config.

Environment variables

Variable	Default	Purpose
`COWORK_QA_HEADED`	unset (headless)	Set to `1` to launch Chromium with a visible window
`COWORK_QA_DATA`	`<cwd>/.cowork-qa`	Directory where `<session-id>.json` traces are written

Usage example

A typical end-to-end loop the orchestrating LLM runs:

Code

session_start({ goal: "find the cheapest 14\" MacBook Pro on apple.com",
                url: "https://www.apple.com/shop/buy-mac/macbook-pro" })
  → { session_id: "abc-123" }

session_observe({ session_id: "abc-123" })
  → URL + aria-snapshot

session_act({ session_id: "abc-123", action: "click",
              target: "button:has-text('Continue')" })

# ... more acts / observes ...

session_end({ session_id: "abc-123" })
  → { steps: 7, trace_path: "~/.cowork-qa/abc-123.json" }

qa_get_trace({ session_id: "abc-123" })
  → Goal: ...
    Steps (7 total): ...
    Final URL: ...
    Final aria-snapshot: ...

Trace format

Each trace is a JSON file:

config.json

{
  "session_id": "abc-123",
  "goal": "...",
  "steps": [
    {
      "t": 142,
      "action": "click",
      "args": { "target": "...", "value": null },
      "url_after": "...",
      "aria_after": "..."
    }
  ],
  "final": { "url": "...", "aria": "..." },
  "path": "/.../abc-123.json"
}

Limitations / known quirks

session_observe calls don't show up in the trace's step count — only session_act calls do. The final aria-snapshot is captured at session_end.
eval runs the JS expression but doesn't return the value to the caller — only side effects on the page are observable.
One Chromium process is shared across all sessions in a server instance; each session gets its own context (cookies, etc. are isolated).
Selectors are passed straight to Playwright. CSS, text-selectors (button:has-text("Send")), and role= selectors all work.

License

MIT — see LICENSE.

Contributing

PRs welcome. Keep it small: this is meant to stay a thin, auditable server.