calc_eval · TOOL4LM MCP: Risk & Policy

WHAT IT DOES

What calc_eval does on TOOL4LM

AI agents invoke calc_eval to trigger actions in TOOL4LM. 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 calc_eval needs a policy

A calculator 'eval' function typically executes expression evaluation, which depending on implementation could run arbitrary code. The name 'eval' strongly implies execution of expressions or code. The description is minimal ('Alias of calc.eval'), so confidence is moderate, but 'eval' semantics are inherently Execute-category.

From the tool's definition 'calc_eval' and 'Alias of calc.eval' — evaluates expressions, likely via a math/code evaluation engine

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

calc_eval Rate-limited

calc_eval 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": {
    "calc_eval": {
      "limits": [
        {
          "counter": "calc_eval_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 TOOL4LM, so you can run agents against it safely.

FAQ

Questions about calc_eval

What does the calc_eval tool do? +

Alias of calc.eval. It is categorised as a Execute tool in the TOOL4LM MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on calc_eval? +

Register the TOOL4LM MCP server in PolicyLayer and add a rule for calc_eval: 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 TOOL4LM. Nothing to install.

What risk level is calc_eval? +

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

Can I rate-limit calc_eval? +

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

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

calc_eval is provided by the TOOL4LM MCP server (khanhs-234/tool4lm). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.