Marketplace Finder — an MCP server that searches marketplaces in your own browser

One job: let a remote agent (e.g. claude.ai) search online marketplaces for an item — anything for sale, not just housing — through your logged-in browser, running on your machine.

How it fits together

claude.ai  ──HTTPS──▶  tunnel (cloudflared/ngrok)  ──▶  this server (your Mac)
                                                            │
                                                            ▼
                                              your logged-in Chromium (Playwright)
                                                            │
                                                            ▼
                                                   Facebook Marketplace

claude.ai can only reach an MCP server over HTTP, but Facebook Marketplace only shows real results to a real, logged-in browser. So this server runs locally (Streamable-HTTP transport), drives your persistent logged-in Chromium, and you expose it to claude.ai through a tunnel.

The agent gathers missing details from you in chat (budget, city, condition…) before it calls a tool — the tools just declare parameters.

Tools the agent gets

• search_facebook_marketplace — query, city, min_price, max_price, radius_km, days_listed, sort (best/newest/price_low/price_high/distance), max_results. Returns structured listings (title, price, location, url, photo, raw text) pulled straight off the results page.
• get_listing_details — full description / condition for one listing URL.

Setup

Just want the full walkthrough? See DEPLOY.md — every step from zero to asking claude.ai to search Marketplace for you (install, login, tunnel, claude.ai connector, daily restart routine, troubleshooting).

python3 -m venv .venv && . .venv/bin/activate
pip install -r requirements.txt
python -m playwright install chromium

python server.py login     # one-time: sign into Facebook, then close the window
python server.py serve      # starts the MCP server on http://localhost:8000/mcp

Then expose it and register it with claude.ai:

cloudflared tunnel --protocol http2 --url http://localhost:8000
#   (or:  ngrok http 8000)

In claude.ai → Settings → Connectors → Add custom connector, paste the tunnel URL with the MCP path:

https://<your-tunnel-host>/mcp

Now ask claude.ai things like "find me a used Herman Miller Aeron under $400 in Seattle, listed this week." It will ask for anything it's missing, then call the search tool, which runs in your browser.

Config (environment variables, all optional)

Var	Default	Meaning
MCP_HOST	127.0.0.1	bind address
MCP_PORT	8000	port
MCP_AUTH_TOKEN	(unset)	if set, require Authorization: Bearer <token>
MCP_ALLOWED_HOSTS	(unset)	comma-separated Host allow-list. Unset = DNS-rebinding protection off (needed so a rotating tunnel host isn't rejected with HTTP 421). Set it to pin specific hosts.
FB_HEADLESS	1	set 0 to watch the browser while serving
FB_DEFAULT_CITY	vancouver	FB city slug used when a search omits one

If MCP_AUTH_TOKEN is unset the endpoint is open — keep your tunnel URL private, or set a token. (claude.ai connectors that support a bearer/OAuth secret can pass it.)

Notes & next steps

• Facebook city slugs are short names like vancouver, seattle, nyc, la, chicago. The agent passes one as city.
• Session expiry: if Facebook starts showing a login wall, the tool says so — re-run python server.py login.
• Adding marketplaces (Craigslist, eBay, Kijiji…): add a new @mcp.tool() in server.py that builds that site's search URL and reuses the same card-extraction pattern. Craigslist needs no login; it's scraped through the same real browser because it blocks datacenter IPs.
• Clarifying questions are handled by the agent today. If you later want the server to drive structured prompts, that's MCP "elicitation" — a tool can request input mid-call via ctx.elicit(...); client support is still uneven.

This folder is self-contained and ready to move into its own repo.