LeftGlove

Make any website usable by AI agents.

Point an LLM at a web page and it sees 10,000 DOM nodes — nested divs, ARIA wrappers, SVG icons, tracking pixels. It burns tokens parsing noise, hallucinates selectors, and clicks the wrong thing. LeftGlove fixes this.

LeftGlove is an MCP server that gives your agent a structured, validated view of any web page — only the elements that matter, with stable locators and human-readable labels. 90% of the DOM noise disappears. What's left is a clean inventory your agent can actually act on.

Agent: "What can I do on this page?"

LeftGlove (observe tool):
  clickable:
    - "Search" button          [data-testid=search-btn]
    - "Add to Cart"            [data-testid=add-cart]
    - "Next Page" link         [data-testid=pagination-next]
  typable:
    - "Search products" input  [data-testid=search-input]
    - "Zip code" input         [data-testid=zip-field]
  readable:
    - "$29.99"                 [data-testid=price]
    - "In Stock"               [data-testid=availability]

No more guessing. No more document.querySelector roulette.

How It Works

Sieve — A deterministic function injected into the browser page. It walks the DOM, filters structural noise, and returns a typed inventory of every interactive and readable element with its locator, label, bounding box, and element type. Zero LLM calls, zero tokens, pure static analysis.

Toddler Loop — A web UI where a human reviews what the sieve found and classifies elements: what matters, what's chrome, what to skip. The output is a glossary that maps intent to concrete page elements. Optional auto-classify via Claude Haiku for bulk labeling.

MCP Server — Exposes the sieve and glossary as tools over the Model Context Protocol. Any MCP client — Claude Desktop, Claude Code, OpenClaw, your own agent — calls observe and gets back structured page state instead of raw HTML.

Quick Start

npx leftglove

That's it. Playwright downloads a bundled Chromium on first run. No Docker, no JVM, no external dependencies.

Claude Desktop / Claude Code

Add to your MCP config:

{
  "mcpServers": {
    "leftglove": {
      "command": "npx",
      "args": ["leftglove"]
    }
  }
}

From source

git clone https://github.com/stephenchilcote-gauntlet/leftglove.git
cd leftglove/leftglove/mcp-server
npm install && npm run build
node dist/index.js

Environment variables

Variable	Default	Description
SIEVE_URL	(auto-start)	URL of an external sieve server. If unset, LeftGlove starts its own Playwright browser.
SIEVE_PORT	3333	Port for the built-in sieve server.
SIEVE_HEADLESS	true	Set to false to see the browser window.

MCP Tools

Tool	Description
observe	Run the sieve on the current page. Returns a structured inventory of interactive elements — clickable, typable, readable — with locators and labels.
click	Click an element by its index from the last observe result.
fill	Fill a text input by its index from the last observe result.
navigate	Navigate the browser to a URL.
screenshot	Take a screenshot of the current page (base64 PNG).
list_vocabulary	List the glossary: intent regions, elements, applicable verbs, and testid locators.
refresh_vocabulary	Reload glossary files from disk after edits.

Why Not Just Feed the HTML to the LLM?

	Raw HTML	LeftGlove
Tokens	50k-200k per page	500-2k
Accuracy	LLM guesses selectors	Validated locators
Cost	$0.10-0.50 per page view	~$0.005
Reliability	Hallucinated clicks	Deterministic inventory

Repository Layout

Path	What
leftglove/mcp-server/	TypeScript MCP server (stdio transport)
leftglove/toddler/	Toddler loop UI — Node.js web app for human classification
leftglove/demo-app/	Demo web app for testing and development
bin/	demo-run — starts all services; demo-test — runs e2e tests

Tech Stack

• MCP Server: TypeScript, @modelcontextprotocol/sdk, Zod
• Sieve: Vanilla JavaScript, runs in-browser via Playwright
• Toddler UI: Node.js, vanilla JS/HTML/CSS
• Testing: Playwright, fast-check (property-based testing)

Status

Pre-release. The sieve, toddler loop, and MCP server work end-to-end. We're actively building toward a packaged release.

License

MIT