Pinback

Comment on your page.
Your agent reads it.

Pinback is a Chrome extension that lets you pin comments to elements on any web page, plus a local MCP server that lets your coding agent read them and make the changes.

Get the extension
localhost:5173 yoursite.com 1 <button> #app › div › button “Make this bigger” Add comment your agent > Hey, check my pinback comments ● get_comments 1 · “Make this bigger” #app › div › button editing button.css… ✓ resolved

Iterate on your build without describing it

If you're anything like me when you're building a site or prototype locally and iterating with an agent, you find yourself screenshotting, or typing "the second button in the header, no, the other one". It can be slow and frustrating. That's where Pinback comes in: you click the exact thing on the page and say what you want. Each comment carries the exact element, so your agent knows precisely what you mean.

  1. Run your app locally and open it in Chrome. Click the Pinback icon and enable it for the tab.
  2. Pin comments to anything on the page: "make this bigger", "wrong green", "this overlaps on mobile".
  3. Ask your agent: Grab my Pinback comments. It reads each comment, with its element selector, through the MCP server.
  4. Comments resolve as your agent works through them. Reload, look at the result, drop the next round of comments.

It's not just for local builds. Annotate any site to collect structured, element-anchored notes for your agent to work from. Useful for competitor teardowns, PRDs, design reviews and content audits.

How it works

Chrome extension pins + comments
→
Local collector 127.0.0.1:57463
→
Your agent MCP tools

The pinback-mcp server runs on your machine, started and stopped by your agent itself. It's a plain stdio MCP server, so it works with Claude Code, Codex, or anything else that speaks MCP. It embeds a small HTTP collector that only listens on localhost. The extension syncs your comments to it; your agent reads them through MCP tools (get_comments, list_origins, resolve_comment, clear_comments).

Quick start

Install the extension from the Chrome Web Store. A setup guide opens automatically and walks you through the following:

  1. Register the MCP server, one command that the guide has you run in a terminal, or paste straight into a chat if you use a desktop app. Claude Code: 
    claude mcp add --scope user pinback -- npx -y pinback-mcp
    Codex: 
    codex mcp add pinback -- npx -y pinback-mcp
    Any other MCP client: register npx -y pinback-mcp as a stdio server named pinback.
  2. Pair the extension. Ask your agent for a pairing code and enter it on the setup page. You'll be commenting in a couple of minutes.

Privacy

Local only

The collector binds to 127.0.0.1, so it is never reachable from the network. Your comments live in ~/.claudback/ on your own machine. No remote servers, no accounts, no analytics.

Paired & permissioned

Every request needs the pairing token, and only the extension's own origin passes CORS, so a random web page can't write into your comment store. Pairing itself uses a short-lived, single-use code (10-minute expiry, five-attempt cap), so the long-lived token never appears in a chat. The extension is off by default and enabled per tab, with per-site permissions granted only when you ask.

Pull, not push

Comments never enter your agent's context automatically. It reads them only when you ask it to call the tools, and each comment is wrapped in an untrusted-data envelope.