Browser CDP

Control a real browser through a Chrome DevTools Protocol proxy.

Overview

This skill provides browser automation via a lightweight HTTP proxy that wraps CDP. The proxy exposes REST endpoints for navigation, screenshots, JS evaluation, clicking, and more — no Playwright/Puppeteer dependency needed.

Prerequisites

Install the required Python dependency:

pip install psutil

A CDP proxy must be running on http://localhost:3456. Start it from the repository root with:

python3 skills/browser-cdp/scripts/cdp_proxy.py

This launches Chrome/Edge with remote debugging enabled and proxies CDP commands over HTTP.

When to Use

✅ USE this skill when:

• "Open this URL and tell me what's on the page"
• "Take a screenshot of the current page"
• "Run this JavaScript on the page"
• "Click the button that says..."
• "Search for and install a Chrome extension"
• "Log into this site and do something"
• Any task requiring a real browser context

❌ DON'T use this skill when:

• Simple HTTP API calls → use curl directly
• Downloading files → use curl -O
• Parsing HTML from a saved file → use python3 with BeautifulSoup
• No CDP proxy running → ask the user to start it first

API Reference

All endpoints are relative to http://localhost:3456.

GET /targets

List all open browser tabs.

curl -s http://localhost:3456/targets | python3 -m json.tool

Response:

[
  { "id": "ABC123", "title": "Google", "url": "https://google.com" }
]

GET /navigate?url=

Navigate a tab to a URL. Uses the most recently created tab, or specify ?target=<targetId>.

curl -s "http://localhost:3456/navigate?url=https://example.com"

GET /screenshot

Take a PNG screenshot of the current page.

# Save to file
curl -s -o screenshot.png http://localhost:3456/screenshot

POST /eval

Execute JavaScript in the page. The request body is plain text (not JSON), sent as Content-Type: text/plain.

curl -s -X POST http://localhost:3456/eval \
  -H "Content-Type: text/plain" \
  -d "document.title"

For multi-line scripts, pipe from stdin or use a heredoc:

curl -s -X POST http://localhost:3456/eval \
  -H "Content-Type: text/plain" \
  -d "JSON.stringify(Array.from(document.querySelectorAll('a')).map(a => ({text: a.innerText, href: a.href})))"

GET /click?selector=

Click an element matching a CSS selector.

curl -s "http://localhost:3456/click?selector=%23submit-btn"

GET /new

Open a new browser tab and return its target ID.

curl -s http://localhost:3456/new

Response:

{ "id": "NEW_TAB_ID", "title": "about:blank", "url": "about:blank" }

Common Workflows

Navigate and extract page content

# Open a page
curl -s "http://localhost:3456/navigate?url=https://example.com"

# Extract all text content
curl -s -X POST http://localhost:3456/eval \
  -H "Content-Type: text/plain" \
  -d "document.body.innerText"

# Extract all links
curl -s -X POST http://localhost:3456/eval \
  -H "Content-Type: text/plain" \
  -d "JSON.stringify([...document.querySelectorAll('a')].map(a => ({text: a.textContent.trim(), href: a.href})))"

Take a screenshot

curl -s "http://localhost:3456/navigate?url=https://example.com"
curl -s -o page.png http://localhost:3456/screenshot

Search and install a Chrome extension

# Search the Chrome Web Store (no login required for search)
curl -s "http://localhost:3456/navigate?url=https://chromewebstore.google.com/search/example%20extension"

# Extract extension IDs from search results
curl -s -X POST http://localhost:3456/eval \
  -H "Content-Type: text/plain" \
  -d "JSON.stringify([...document.querySelectorAll('a[data-id]')].map(a => ({id: a.dataset.id, title: a.textContent.trim()})))"

# Install an extension (requires the extension ID)
curl -s "http://localhost:3456/navigate?url=https://chromewebstore.google.com/detail/<extension-id>"
# Then click the "Add to Chrome" button
curl -s "http://localhost:3456/click?selector=%5Bdata-id%3Dinstall-button%5D"

Fill a form and submit

# Navigate to the form
curl -s "http://localhost:3456/navigate?url=https://example.com/login"

# Fill in fields
curl -s -X POST http://localhost:3456/eval \
  -H "Content-Type: text/plain" \
  -d "document.querySelector('#username').value = 'myuser'"
curl -s -X POST http://localhost:3456/eval \
  -H "Content-Type: text/plain" \
  -d "document.querySelector('#password').value = 'mypass'"

# Submit
curl -s "http://localhost:3456/click?selector=%23login-form+%3E+button"

Notes

• The CDP proxy must be running before using any commands
• If the proxy is not running, ask the user to start it: python3 skills/browser-cdp/scripts/cdp_proxy.py
• Use URL encoding for query parameters with special characters
• The /eval endpoint returns the result of the last expression (like a REPL)
• Screenshots are returned as PNG binary data
• For complex multi-step interactions, chain /eval and /click calls
• The proxy supports a ?target=<targetId> parameter on most endpoints to target a specific tab