marktplaats-mcp

A read-only MCP server for marktplaats.nl, the Dutch classifieds site. It lets an agent search listings and read price, specs, condition, delivery method, location and seller.

Built with the har-to-mcp skill: the site's own browser traffic was recorded once, then the internal API was called directly. No browser runs at query time.

Status

Capture date: 2026-08-16. Verified against the live site the same day: 42 client checks and 14 MCP protocol checks, all passing.

Consumer sites change. Re-record when tools start failing. See "Re-recording" below.

Related MCP server: opensooq-mcp

Credentials

None. Every tool is a public, logged-out GET request. There are no tokens, no cookies, no accounts, and nothing to refresh.

This is the whole reason the server is simple. Read-only public search needs no session.

No environment variable is required. Two optional ones tune the rate limiter, below.

Rate limiting

This reads an internal API on a live consumer site, so the client is built to behave politely rather than quickly.

• Requests are serialised with a minimum gap between them. If an agent fires eight searches at once they queue into one orderly stream instead of fanning out.

• Throttling and transient 5xx are retried with exponential backoff and jitter, honouring Retry-After when the site sends it.

The defaults are deliberately conservative. If bulk work feels slow, do less of it rather than turning the gap down. If the site starts returning HTTP 429, raise MARKTPLAATS_MIN_INTERVAL_MS instead of retrying harder.

Install

Requires Node.js 20 or newer.

git clone <this-repo-url> marktplaats-mcp
cd marktplaats-mcp
npm install
npm run build

Register with Claude Code. Run this from the repo root and it fills in the path for you:

claude mcp add marktplaats -- node "$PWD/dist/server.js"

Or add it to any MCP client config, using an absolute path to your clone:

{
  "mcpServers": {
    "marktplaats": {
      "command": "node",
      "args": ["/absolute/path/to/marktplaats-mcp/dist/server.js"]
    }
  }
}

Check it works:

npm run test:mcp

Tools

search_listings

Search the site. This is the primary tool and it already carries price, specs and delivery, so most questions need only this one call.

get_listing

Full detail for one listing, by id (a1517154667) or URL. Adds what search does not carry: shipping carrier and transit days, view count, favourites, listed-since date, seller tenure, category path, bidding and reserved state, CO2 estimate, and the full description.

get_seller

A seller's public profile by numeric seller id. Useful for telling a private seller from a shop.

Field notes

Delivery has three values, not two. shipping (Verzenden), pickup (Ophalen), and both (Ophalen of Verzenden). both is the most common value on the site, at roughly 13 of every 30 results. Filtering by delivery: "shipping" also returns both listings, which is correct, because those sellers will ship. Only shipping and pickup are filterable; the site has no filter for both.

Price can be absent. priceEur is null when the listing takes bids, is free, or names no price. Read priceType and priceLabel in that case.

Sponsored results are included and flagged. isSponsored is true for any paid placement. sponsoredType tells them apart: dagtopper is a boosted private listing (the site shows "Topadvertentie"), admarkt is a professional-seller advert. Filter on isSponsored if you want organic results only.

Dutch values are kept. Every translated field has a Raw twin: condition and conditionRaw, delivery and deliveryRaw. Use the raw value to check a translation against what the site shows.

limit is enforced by this client, not the site. The search API injects sponsored placements on top of the requested limit, so limit=3 can return 18 rows. The client slices back to the requested count, keeping the site's own ordering.

How it works

The site is server-rendered Next.js. It has no public API. Two internal routes carry everything:

Filters map to query parameters like this:

• Price is a range facet: attributeRanges[]=PriceCents:<from>:<to>. A plain PriceCentsFrom is silently ignored.

• Condition and delivery are attribute ids: attributesById[]=30 and similar. Confirmed live: Nieuw 30, Zo goed als nieuw 31, Gebruikt 32, Niet werkend 13940, Refurbished 14050, Ophalen 33, Verzenden 34.

• Distance is postcode=1011AB&distanceMeters=5000.

What is fragile

Everything above comes from JSON except two reads on the detail page. get_listing parses the rendered HTML for the spec table (Attributes-module-item) and the description (Description-module-description). Those two are the first things to break if the site restyles.

If they break, get_listing still returns price, seller, category, shipping, stats and flags, because those come from window.__CONFIG__. search_listings does not depend on any DOM parsing at all.

The AWS WAF bot-control SDK is present on the site. It did not challenge plain HTTP requests during the capture or during verification. If it starts to, the tools will surface the HTTP status in the error message.

Testing

npm test             # both suites
npm run test:client  # 42 checks against the live site
npm run test:mcp     # 14 checks over the real MCP stdio protocol

Both are read-only and safe to run. They hit the live site, so they need network access and take about a minute.

CI mirrors that split. Type check and build run on every push and never touch the site. The live suites run weekly, as an early warning that the site changed.

Call a tool by hand without wiring up a client:

npm run ask -- search '{"query":"iphone 15 pro","maxPriceEur":500}'
npm run ask -- listing a1517154667
npm run ask -- seller 57429132

Re-recording

If the site changes, re-run the capture and re-check the parsing.

Capture drives a real browser, so it needs Playwright. The MCP server does not, which is why Playwright is not a dependency of this package and a normal install stays small. Install it only when you need to re-record:

npm install -D playwright
npx playwright install chromium
npm run capture     # drives a headless Chromium over the public search flow

Already have Playwright elsewhere? Point at it instead of installing a second copy:

MARKTPLAATS_PLAYWRIGHT=/path/to/node_modules/playwright npm run capture

The HAR lands in captures/ and screenshots in shots/. Both are gitignored, and must stay that way. A HAR records real request headers, so yours will contain your own consent, WAF and analytics cookies. The capture never logs in, so these are anonymous identifiers rather than account credentials, but they still identify your browser session. Never commit a HAR, and never git add -f those directories.

Then follow the har-to-mcp skill from Phase 1.

Project layout

src/client.ts     typed HTTP client for marktplaats.nl, knows nothing about MCP
src/server.ts     the MCP surface, contains no parsing
scripts/verify.mjs      client checks against the live site
scripts/smoke-mcp.mjs   checks over the real MCP stdio protocol
scripts/capture.mjs     re-records the HAR, needs Playwright
scripts/ask.mjs         call a tool from the shell

Keeping the two src files apart is deliberate. Parsing changes stay in client.ts, and the tool surface in server.ts stays stable.

captures/, shots/ and work/ are gitignored build-time artefacts and never ship.

Scope

Read-only, by design. Nothing here logs in, posts an advert, places a bid, messages a seller, adds to a cart, or buys. Every tool is a GET and is annotated readOnlyHint: true.

Automated access may sit outside the site's terms of service. You are responsible for how you use it. Keep request rates low and sane.

This is an unofficial client. It is not affiliated with, endorsed by, or supported by Marktplaats or its owners.

Contributing

Contributions are welcome. See CONTRIBUTING.md for setup, tests and the review rules. The short version: keep it read-only, keep request rates low, and never commit a capture.

• Code of conduct: CODE_OF_CONDUCT.md

• Security issues: SECURITY.md, reported privately, never as a public issue

• Release history: CHANGELOG.md

If a tool stopped working, that is usually the site changing rather than a code bug. Open a A tool stopped working issue; the template collects what is needed to tell the two apart.

License

ISC.