Style Capture

Style Capture

Capture computed CSS and HTML from a live web page, map it to Tailwind utilities, and output a structured <style_capture> prompt for faithful UI recreation.

Workflow

Browser tool: Always use the agent-browser CLI for all browser interactions. Never use Chrome MCP, "Claude in Chrome", or any other browser automation tool.

Every capture follows this pattern:

Capture progress:
- [ ] Step 1: Open the page
- [ ] Step 2: Find the target element
- [ ] Step 3: Get the CSS selector
- [ ] Step 4: Capture styles

Step 1: Open the page

agent-browser open <url> && agent-browser wait --load networkidle

Step 2: Find the element

Use agent-browser eval to locate the element by the user's description and return its parent container's selector. This is the most reliable approach — it runs JavaScript directly in the page:

agent-browser eval "(() => {
  const el = Array.from(document.querySelectorAll('h2, h1, section, [class]'))
    .find(el => el.textContent.includes('TARGET TEXT'));
  if (!el) return null;
  // Walk up to the nearest section/container
  const container = el.closest('section') || el.parentElement;
  return {
    tag: container.tagName,
    id: container.id,
    classes: container.className,
    selector: container.id ? '#' + container.id : container.tagName.toLowerCase() + '.' + container.className.split(' ')[0]
  };
})()"

If the text-based approach doesn't work, fall back to the snapshot:

agent-browser snapshot -i

Read the snapshot output and identify which @e ref matches the user's description. Match by tag name, text content, role, or surrounding context.

If the element isn't visible in the snapshot, scroll to it or scope the snapshot:

agent-browser scrollintoview @e<N>
agent-browser snapshot -i -s "main"

For visual identification when there are too many elements:

agent-browser screenshot --annotate

Step 3: Get the CSS selector

Once you've identified the element (via eval result or @e ref), get its HTML:

agent-browser get html @e<N>
# or for a known selector:
agent-browser get html "section.ClassName"

Build a CSS selector. Prefer in order:

1. #id if the element has an id 2. A unique class combination like .hero-section or section.CTA_prefooter__abc 3. A structural selector like section:nth-child(2) or main > div > h1

Step 4: Capture styles

Run the capture CLI with the URL and derived CSS selector:

npx style-capture "<url>" "<css-selector>"

Options:

• --mode curated (default) — common visual CSS properties only
• --mode full — all computed styles

Arguments

$ARGUMENTS is parsed as: <url> [natural language element description]

• First argument: the URL
• Remaining arguments: natural language description of the target element

Examples:

• /style-capture https://stripe.com the pricing table
• /style-capture https://linear.app the hero section with the gradient
• /style-capture https://vercel.com/dashboard the sidebar navigation

If only a URL is provided, ask the user which element they want to capture.

Output

The output is a <style_capture> XML block containing:

• html_capture — sanitized, annotated HTML of the subtree
• css_capture — computed CSS grouped by element
• tailwind_hints — suggested Tailwind utility classes with confidence scores
• open_questions — low-confidence mappings flagged for review

Use this output to faithfully recreate or refactor the captured UI in code.

agent-browser command reference

Only use these commands — do not guess command names:

Wrong commands: evaluate, exec, execute, run — these do not exist. The JavaScript command is eval.

Tips

• For complex pages, start with a broader element (e.g. a whole section) rather than individual elements
• Use --mode full when you need exact CSS fidelity including all computed properties
• If the element is inside a shadow DOM or iframe, you may need to capture a parent element instead
• After capture, the browser session stays open — you can capture additional elements without reopening