preview · 3D MCP Server MCP: Risk & Policy

WHAT IT DOES

What preview does on 3D MCP Server

AI agents invoke preview to trigger actions in 3D MCP Server. 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 preview needs a policy

This tool executes an external OpenSCAD process to render the current 3D scene into a PNG image. It is not a simple read/query of existing data, nor does it modify stored model data — it triggers an external execution (OpenSCAD binary) whose output depends on the current scene state. The blast radius is medium since it consumes compute resources and writes a file, but does not delete or move money.

From the tool's definition 'Render a PNG preview image' — triggers OpenSCAD rendering process externally

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

preview Rate-limited

preview 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": {
    "preview": {
      "limits": [
        {
          "counter": "preview_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 3D MCP Server, so you can run agents against it safely.

FAQ

Questions about preview

What does the preview tool do? +

Render a PNG preview image of the current scene (requires OpenSCAD). It is categorised as a Execute tool in the 3D MCP Server MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on preview? +

Register the 3D MCP Server MCP server in PolicyLayer and add a rule for preview: 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 3D MCP Server. Nothing to install.

What risk level is preview? +

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

Can I rate-limit preview? +

Yes. Add a rate_limit block to the preview 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 preview completely? +

Set action: deny in the PolicyLayer policy for preview. 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 preview? +

preview is provided by the 3D MCP Server MCP server (jagjerez-org/3d-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.