Built-in AI Agent that builds custom Add-ons from user's plain-language requests, using MCP

[barbaros]

Plain-language version (for non-technical readers)

The problem today

• If you want Firefox to do something extra — tidy your tabs, compare pages, tidy bookmarks — you either hunt for an existing Add-on (a small plugin someone else built) or learn to code one yourself
• Most people can't do either, so they just live with the mess

What this feature would do

You'd type what you want in plain language, and an AI Agent built into Firefox would either do it directly or build a small custom tool that does it from then on. Some examples:

Tab management

• "Close all my duplicate tabs" — Agent finds tabs pointing to the same page and shuts the extras
• "Group my tabs by topic — work stuff together, shopping together, news together" — Agent reads what each tab is about and sorts them into named groups
• "Sort my tabs alphabetically" or "put the oldest tabs first" — simple housekeeping, done instantly

Reading and comparing across tabs

• "Compare the prices on these three tabs and tell me which is cheapest" — Agent reads all three pages and gives you a straight answer
• "Summarise the differences between these two recipes" — same idea, applied to any content
• "Which of these five job listings pays the most?" — Agent scans all open tabs and reports back

Talking to a website like it's part of the conversation

• Open an article, then just ask "what does this say about side effects?" — no copy-pasting, the Agent already has the page in view, the same way it would remember something you'd typed earlier in a chat
• Works for one page, or several open at once

Asking questions across a whole website, not just one page

• "Search this entire documentation site and tell me how to reset a password" — the Agent doesn't just read the page you're on; it can look through every page on that site (this is similar to how AI search tools dig through a whole knowledge base rather than a single document) and combine the answer
• Useful for manuals, support sites, or long guides split across many pages

Bookmarks

• "Tidy my bookmarks — merge duplicates and put everything into proper folders" — Agent reorganises years of clutter in one go
• "Find bookmarks I haven't opened in over a year and ask me before deleting them" — cleanup, but cautious

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You're always the one in control

However clever the request, nothing happens without your say-so:

• Before the Agent closes a tab, moves a bookmark, or installs anything, it shows you exactly what it's about to do in plain English
• You approve or decline each action — or set rules once (e.g. "always OK to close duplicate tabs, but always ask before touching bookmarks")
• Everything the Agent does can be undone with one click — closed tabs restored, bookmarks put back, custom tools removed
• If you ever want to stop it entirely, one switch turns the Agent off completely, and Firefox goes back to behaving exactly as it does today

Why this matters

• Removes the coding barrier — most people who'd benefit from a custom browser tweak can't write one
• Faster than searching the Add-ons store for a niche behaviour that may not exist
• Transparent and reversible — unlike installing a random third-party extension of unknown origin, the code is generated fresh, inspectable, and scoped to only the permissions it needs

For Firefox triage (technical)

• Add a native Agent Mode Interface to Firefox that can read and act on user instructions typed in plain English
• The Agent connects to Firefox's WebExtension API (the toolkit that lets Add-ons — also called extensions or plugins — change how the browser behaves) via MCP (Model Context Protocol — a standard way for an AI agent to discover and call a set of tools/functions safely, rather than guessing at code)
• Instead of the user writing JavaScript and manifest files by hand, they describe the behaviour they want, and the Agent:
  1. Interprets the request
  2. Asks the user which content to manipulate: Tabs, Bookmarks, History, etc.
  3. Generates the necessary Add-on code (background scripts, content scripts, permissions, manifest.json)
  4. Installs it locally in a sandboxed/temporary state for review
  5. Asks for explicit user confirmation before final installation
• All these can be done easily with the current libraries but someone has to put that code in Firefox. Feel free to check those libraries: CrewAI, LangChain

[Jon]

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