Render MCP Server

render-mcp

Gives an AI agent a real browser. Screenshots, PDFs, and the HTML a page produces after JavaScript has run.

No API key. No signup. No account. Point your client at a URL and it works.

https://render.makermargins.com/mcp

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Why this exists

An agent can fetch a URL. It cannot see one.

Ask an assistant to check whether a page looks right, or to read a site built with React, and it hits a wall: a plain HTTP fetch returns an empty shell and a loading spinner. The content is built by JavaScript that never runs.

The usual answer is a rendering API — but every one of them requires you to sign up, verify an email, and paste an API key. An agent working on its own can't do any of that. It has no inbox and no card. A free tier it cannot register for is worth nothing to it.

This server needs none of it. It runs on Cloudflare's network, launches a real headless browser, and hands back what the page actually looks like.

Install

Claude Code — as a plugin (one command, and updates arrive automatically)

/plugin marketplace add RodRomer/render-mcp
/plugin install render@render-mcp

Claude Code — directly

claude mcp add --transport http render https://render.makermargins.com/mcp

Claude Desktop, Cursor, and other clients — add to your MCP config:

{
  "mcpServers": {
    "render": {
      "type": "http",
      "url": "https://render.makermargins.com/mcp"
    }
  }
}

That's the whole setup. Nothing to install, nothing to configure, no credentials.

Tools

screenshot_url

See a page as a person would. Returns a PNG.

Good for: confirming a deployment looks right, checking a layout, seeing what a user sees.

rendered_html

The DOM after JavaScript has executed. Returns HTML text.

Good for: single-page apps, anything where a plain fetch returns a shell.

page_diagnostics

Load a page and report what went wrong: JavaScript console errors, failed network requests, and any 4xx/5xx responses. Returns a readable summary.

Good for: a deployment that might have shipped a bug, a page that loads blank, a site that "looks broken" and you need to know why. An agent cannot see a browser console any other way.

Playwright MCP can do this too — but it must be installed locally, with Node and browser binaries present, and its HTTP mode has known session bugs. This runs hosted, stateless, with nothing to install.

inspect_element

Answers "why isn't this element showing where I expect?" for a CSS selector.

Leads with a diagnosis, then the numbers: resolved box model, computed display / visibility / opacity / position / z-index, colours, whether it's inside the viewport, and whether another element is covering it.

The useful part is that it walks up the tree. The usual reason an element is missing is not the element — it's an ancestor, and the answer you want is which one:

--- match 1: button#buy
  HIDDEN BY AN ANCESTOR — div.modal.panel has display:none. The element itself is fine.

It also catches the case no single property reveals. Content inside a closed <details> keeps a normal box and reports display:block, visibility:visible, opacity:1 — everything looks fine, and it still doesn't paint:

  NOT RENDERED — it sits inside details.fees, which is not displaying its
  contents because of a closed <details>.
  Box: 70x27 ...  display:block  visibility:visible  opacity:1

Good for: an element that "should be there", a click landing on the wrong thing, verifying a CSS change actually applied. Cascade resolution and layout cannot be derived from reading HTML and CSS — this is the one thing a browser is strictly required for.

url_to_pdf

Render a page to PDF as a browser would print it.

Good for: archiving a page, turning a rendered report into a document.

What it won't do

Stated plainly, so an agent doesn't waste calls discovering them:

• No private networks. Loopback, RFC1918 ranges, 169.254.x.x, .internal and .local hostnames are refused. This server runs inside Cloudflare's network and an unvalidated URL would be a server-side request forgery.
• No logins. There's no session, so anything behind authentication renders as its login page.
• 20 second navigation limit. Very slow pages will time out.
• No JavaScript injection. It renders pages; it doesn't run your code on them.

Failures come back as readable text explaining what went wrong, not as protocol errors — so an agent can route around them rather than crashing.

Privacy

URLs and page content are never stored or logged. Each call launches a browser, does the work, hands back the result, and closes it. Nothing about what you asked for is retained.

One thing is counted, and it's worth stating precisely rather than hiding behind "anonymised":

That's three fields with no way to tie them to a request, a person or a site. The function that writes them is never handed the URL in the first place, so it cannot record one by accident — see count() in src/index.js.

It exists for one reason: this server is free, and the only way to decide whether it's worth keeping alive is knowing whether anything calls it.

The counts are public — no login, no dashboard:

https://render.makermargins.com/stats

Development

npm install
npm test          # 279 tests, no network or browser needed
npm run test:dom  # 39 DOM tests, headless Edge/Chrome, no network
npm run dev       # local worker
npm run deploy    # to Cloudflare

Two layers, both tested outside their host:

• src/protocol.js — the MCP request/response surface as pure functions, with no Cloudflare or browser dependency. Every URL validation and SSRF rule is proven under plain Node before anything deploys.
• src/inspect-page.js — the half of inspect_element that runs inside the page. It closes over nothing, so any real DOM can execute it. Its tests build fixture pages in headless Edge and assert on real computed styles and real geometry. A mocked DOM would prove nothing here: the entire premise of the tool is that these values only exist once a browser has resolved the cascade and run layout.

src/index.js is a thin shell — transport in, browser work out, prose formatting on the way back.

If Node isn't installed, npm run test:nonode runs the protocol suite in headless Edge instead. It strips only the export/import keywords and executes the same source.

When testing against a live page, use a neutral URL

Use https://example.com — it is reserved by IANA for exactly this — or httpstat.us for error paths. Do not point live tests at makermargins.com.

The reason is not politeness. That site has Cloudflare Web Analytics, whose beacon is injected into HTML responses for browser-like requests. This server drives a real headless browser, so every screenshot or audit of that site executes the beacon and registers as a visitor — inflating the traffic figures of the very asset the numbers are meant to measure. An instrument that counts its own operator measures nothing.

Status

Early and free. Built to find out whether MCP registry discovery actually works. If it gets used, it'll be maintained; if it doesn't, that's a useful answer too.

Issues and pull requests welcome.

Licence

MIT