Browser Tools skill

Browser Tools

Chrome DevTools Protocol tools for agent-assisted web automation. These tools connect to Chrome running on :9222 with remote debugging enabled.

Setup

Run once before first use:

cd {baseDir}/browser-tools
npm install

Start Chrome

{baseDir}/browser-start.js              # Fresh profile
{baseDir}/browser-start.js --profile    # Copy user's profile (cookies, logins)

Launch Chrome with remote debugging on :9222. Use --profile to preserve user's authentication state.

Navigate

{baseDir}/browser-nav.js https://example.com
{baseDir}/browser-nav.js https://example.com --new

Navigate to URLs. Use --new flag to open in a new tab instead of reusing current tab.

Evaluate JavaScript

{baseDir}/browser-eval.js 'document.title'
{baseDir}/browser-eval.js 'document.querySelectorAll("a").length'

Execute JavaScript in the active tab. Code runs in async context. Use this to extract data, inspect page state, or perform DOM operations programmatically.

Screenshot

{baseDir}/browser-screenshot.js

Capture current viewport and return temporary file path. Use this to visually inspect page state or verify UI changes.

Pick Elements

{baseDir}/browser-pick.js "Click the submit button"

IMPORTANT: Use this tool when the user wants to select specific DOM elements on the page. This launches an interactive picker that lets the user click elements to select them. The user can select multiple elements (Cmd/Ctrl+Click) and press Enter when done. The tool returns CSS selectors for the selected elements.

Common use cases:

• User says "I want to click that button" → Use this tool to let them select it
• User says "extract data from these items" → Use this tool to let them select the elements
• When you need specific selectors but the page structure is complex or ambiguous

Cookies

{baseDir}/browser-cookies.js

Display all cookies for the current tab including domain, path, httpOnly, and secure flags. Use this to debug authentication issues or inspect session state.

Extract Page Content

{baseDir}/browser-content.js https://example.com

Navigate to a URL and extract readable content as markdown. Uses Mozilla Readability for article extraction and Turndown for HTML-to-markdown conversion. Works on pages with JavaScript content (waits for page to load).

When to Use

• Testing frontend code in a real browser
• Interacting with pages that require JavaScript
• When user needs to visually see or interact with a page
• Debugging authentication or session issues
• Scraping dynamic content that requires JS execution

---

Efficiency Guide

DOM Inspection Over Screenshots

Don't take screenshots to see page state. Do parse the DOM directly:

// Get page structure
document.body.innerHTML.slice(0, 5000)

// Find interactive elements
Array.from(document.querySelectorAll('button, input, [role="button"]')).map(e => ({
  id: e.id,
  text: e.textContent.trim(),
  class: e.className
}))

Complex Scripts in Single Calls

Wrap everything in an IIFE to run multi-statement code:

(function() {
  // Multiple operations
  const data = document.querySelector('#target').textContent;
  const buttons = document.querySelectorAll('button');
  
  // Interactions
  buttons[0].click();
  
  // Return results
  return JSON.stringify({ data, buttonCount: buttons.length });
})()

Batch Interactions

Don't make separate calls for each click. Do batch them:

(function() {
  const actions = ["btn1", "btn2", "btn3"];
  actions.forEach(id => document.getElementById(id).click());
  return "Done";
})()

Typing/Input Sequences

(function() {
  const text = "HELLO";
  for (const char of text) {
    document.getElementById("key-" + char).click();
  }
  document.getElementById("submit").click();
  return "Submitted: " + text;
})()

Reading App/Game State

Extract structured state in one call:

(function() {
  const state = {
    score: document.querySelector('.score')?.textContent,
    status: document.querySelector('.status')?.className,
    items: Array.from(document.querySelectorAll('.item')).map(el => ({
      text: el.textContent,
      active: el.classList.contains('active')
    }))
  };
  return JSON.stringify(state, null, 2);
})()

Waiting for Updates

If DOM updates after actions, add a small delay with bash:

sleep 0.5 && {baseDir}/browser-eval.js '...'

Investigate Before Interacting

Always start by understanding the page structure:

(function() {
  return {
    title: document.title,
    forms: document.forms.length,
    buttons: document.querySelectorAll('button').length,
    inputs: document.querySelectorAll('input').length,
    mainContent: document.body.innerHTML.slice(0, 3000)
  };
})()

Then target specific elements based on what you find.