render_html · PageShot MCP: Risk & Policy

WHAT IT DOES

What render_html does on PageShot MCP

AI agents invoke render_html to trigger actions in PageShot MCP. What it does depends on the arguments the agent supplies, and its effects often reach beyond the immediate call — builds kicked off, notifications sent, workflows started.

WHY IT NEEDS A POLICY

Why render_html needs a policy

Rendering arbitrary HTML/CSS is an Execute-class operation: it runs caller-supplied code in a browser/rendering engine. While the primary output is a static image, the rendering step can trigger JavaScript execution, external resource fetches, and other side effects depending on the HTML provided.

From the tool's definition 'Render raw HTML/CSS to an image' — executes arbitrary HTML/CSS content supplied by the caller, triggering a rendering engine to process and run that markup

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

render_html Rate-limited

render_html stays usable, but rate-capped — a runaway agent can't fire it dozens of times a minute. Everything else on the server is denied unless you say otherwise.

View as policy code

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "render_html": {
      "limits": [
        {
          "counter": "render_html_rate",
          "window": "minute",
          "max": 10,
          "scope": "grant"
        }
      ]
    }
  }
}

RATE-LIMIT THIS TOOL →

Instant setup, no code required.

PolicyLayer is an MCP gateway: every tool call is checked against your rule before it reaches PageShot MCP, so you can run agents against it safely.

FAQ

Questions about render_html

What does the render_html tool do? +

Render raw HTML/CSS to an image. Perfect for generating OG images, social cards, email previews, and dynamic content from templates. No URL needed. It is categorised as a Execute tool in the PageShot MCP MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on render_html? +

Register the PageShot MCP server in PolicyLayer and add a rule for render_html: allow, deny, rate-limit, or require approval. Point your MCP client at the PolicyLayer proxy URL and the rule is enforced on every call, before it reaches PageShot MCP. Nothing to install.

What risk level is render_html? +

render_html is a Execute tool with high risk. Execute tools should be rate-limited and have argument validation enabled.

Can I rate-limit render_html? +

Yes. Add a rate_limit block to the render_html rule in your PolicyLayer policy. For example, setting max: 10 and window: 60 limits the tool to 10 calls per minute. Rate limits are tracked per agent session and reset automatically.

How do I block render_html completely? +

Set action: deny in the PolicyLayer policy for render_html. The AI agent will receive a policy violation error and cannot call the tool. You can also include a reason field to explain why the tool is blocked.

What MCP server provides render_html? +

render_html is provided by the PageShot MCP server (pageshot-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.