cowork-qa-mcp

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+.

git clone https://github.com/inSideos-designs/cowork-qa-mcp.git
cd cowork-qa-mcp
npm install     # also installs Chromium via Playwright postinstall
npm run build

Wire into your MCP-compatible client

Claude Code

claude mcp add cowork-qa --scope user -- node /absolute/path/to/cowork-qa-mcp/dist/server.js

To watch the browser instead of running headless:

claude mcp add cowork-qa --scope user \
  -e COWORK_QA_HEADED=1 \
  -- node /absolute/path/to/cowork-qa-mcp/dist/server.js

Other MCP clients

Any MCP client that speaks stdio works. Point it at dist/server.js.

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:

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:

{
  "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.