eval_ruby · Sketchup MCP: Risk & Policy

WHAT IT DOES

What eval_ruby does on SketchupMCP

AI agents invoke eval_ruby to trigger actions in SketchupMCP. 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 eval_ruby needs a policy

This tool executes arbitrary Ruby code within the SketchUp environment, which gives unrestricted programmatic access. An AI agent could use this to run any code including file system operations, network calls, deleting geometry, or other destructive/malicious actions. 'Arbitrary' code execution with no apparent sandboxing is the highest-risk Execute category, warranting critical severity.

From the tool's definition "Evaluate arbitrary Ruby code in Sketchup"

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

eval_ruby Rate-limited

eval_ruby 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": {
    "eval_ruby": {
      "limits": [
        {
          "counter": "eval_ruby_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 SketchupMCP, so you can run agents against it safely.

FAQ

Questions about eval_ruby

What does the eval_ruby tool do? +

Evaluate arbitrary Ruby code in Sketchup. It is categorised as a Execute tool in the SketchupMCP MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on eval_ruby? +

Register the Sketchup MCP server in PolicyLayer and add a rule for eval_ruby: 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 SketchupMCP. Nothing to install.

What risk level is eval_ruby? +

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

Can I rate-limit eval_ruby? +

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

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

eval_ruby is provided by the Sketchup MCP server (piexl/sketchup-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.