UI Inspector

Live preview + element inspector MCP server for Claude Code. Click any DOM element in a running preview and Claude instantly sees the exact element name (component, id, aria-label, …), code location, computed styles, parent chain, and UI/UX terminology — then edits the file directly.

No external LLM calls. All reasoning happens in Claude itself.

Install

cd servers
npm install

Register the MCP server in ~/.claude.json (replace </path/to> with your absolute checkout path):

"ui-inspector": {
  "type": "stdio",
  "command": "node",
  "args": ["</path/to>/ui-inspector/servers/inspector-server.mjs"]
}

Restart Claude Code.

Tools (18)

Preview (8)

• preview_start — new Vite session (react / vue / vanilla template)
• preview_attach — attach to an existing Next.js/Vite/etc. dev server via inject proxy
• preview_update — write/delete files and trigger Vite HMR
• preview_status
• preview_stop
• preview_export — convert to target framework + zip
• preview_screenshot — capture viewport or single selector (mobile / tablet / desktop / full)
• preview_errors — runtime errors captured from the page (uncaught errors, unhandled rejections, console.error)

Inspector (4)

• preview_select_element — enable/disable inspector mode or fetch selection (session-scoped)
• inspector_get_selection — most recent click across all sessions; called when the user says "this", "here", "the selected one"
• inspector_clear_selection
• inspector_highlight — agent → browser visual pointing: flash-highlight an element by CSS selector or data-at value, with optional label ("여기 수정했어요")

Annotations (4) — Agentation-style multi-annotation

• annotation_list — all annotations (pins + comments) left by the user in the browser, with full element context
• annotation_resolve — mark annotations resolved (pins turn green live in the browser) with an optional note; reopen: true to undo
• annotation_remove — delete annotations (ids or all)
• annotation_to_prompt — convert annotations into an agent-ready markdown task list (same format as the in-browser Copy Prompt button — paste into Claude Code, Codex, or any coding agent)

Knowledge (2)

• query_ontology — local design knowledge store
• validate_design — contrast / tap target / hierarchy / spacing rules

Annotations — Agentation-style workflow

The injected toolbar (bottom-right) is a monochrome capsule cluster: a ◉ brand circle (click = exit all modes), a mode capsule with Inspect | Annotate | Manage ▾, and a Copy Prompt (open/total) CTA capsule that inverts on hover. Press ESC any time to exit Inspect/Annotate mode (it first closes an open dialog, pin popup, or menu). The side panel renders as white ticket cards (mono type, red accent) on a near-black ground, and slides the toolbar out of its way.

1. Toggle Annotate and click any element — a comment dialog opens (⌘+Enter to save)
2. A numbered amber pin appears. Add as many annotations as you want — multiple pins on the same element are supported (they stack side-by-side)
3. Drag to batch-select: in Annotate mode, drag a marquee over a region — every top-level element fully inside it gets selected (if the selection collapses to a single wrapper, it descends into its children), then one comment creates a group annotation (one pin, up to 30 elements). The pin popup shows a "요소 N개" chip and outlines every member; the agent receives per-element selectors and source locations
4. Click a pin to edit the comment, resolve/reopen, or delete it
5. Ask the agent to apply them: it calls annotation_list, edits the files, then calls annotation_resolve per item — the pin turns into a green ✓ in real time, with the agent's resolution note in the pin popup
6. Annotations live on the server, so they survive page reloads, navigation, and HMR. Pins re-anchor via data-at → CSS path → selector
7. Pins are page-scoped: each pin only renders on the page (pathname) where it was created — navigating elsewhere hides it, coming back restores it. SPA route changes (pushState) are detected without a reload. The toolbar count and Copy Prompt cover the current page; annotation_list / annotation_to_prompt still return every page (each item carries its pageUrl)
8. No MCP? Press Copy Prompt to copy the current page's annotation set as a markdown task list for any AI coding agent
9. Bulk manage (Manage ▾): resolve or delete all annotations at once, scoped to this page or all pages. Delete is two-click (arms → confirm) to avoid accidents. Counts update live as you work

Each annotation carries: comment, status, element name, robust CSS path, source location (data-at), UI term, computed styles, text, size, and a truncated HTML snippet.

The annotation UI ships with the inject proxy (preview_attach). For preview_start sessions, attach to the Vite URL if you need annotations.

What Claude sees on each click

inspector_get_selection returns:

• sourceLocation — { file, line, column } from the data-at attribute injected by the Vite plugin
• elementName — the exact identifier of the element with priority resolution: id → data-testid → aria-label → aria-labelledby → <label for> → component name (from source filename) → name → alt → title → placeholder → first class → tag. Returned with primary, primarySource, plus the full set (componentName, id, testId, ariaLabel, role, selector, …)
• uiTerm / uiDescription — UI/UX terminology inferred from tag, role, class patterns, and computed-style heuristics (Card, Hero Section, Stack Layout, …)
• tag, className, textContent (truncated)
• boundingRect — { x, y, width, height }
• computedStyles — background, color, font, padding, margin, display, position, size, border-radius, gap
• parentChain — up to the body, with id/first-class shorthand

The information panel that pops up in the browser displays the same data — with the exact name shown prominently at the top alongside the source badge.

Workflow

1. Start or attach a preview (preview_start or preview_attach)
2. Toggle the inspector (bottom-right button in the browser, or preview_select_element with action: enable_inspector)
3. Click an element in the page — the side panel shows its exact name, source location, design term, and styles
4. Ask Claude "change the padding on this"
5. Claude calls inspector_get_selection, reads the file at sourceLocation.file:line, and edits it
6. Vite HMR reloads automatically

See ~/.claude/skills/ui-inspector/SKILL.md for the skill that wires this up.