calculate · Basic MCP: Risk & Policy

WHAT IT DOES

What calculate does on Basic

AI agents invoke calculate to trigger actions in Basic. 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 calculate needs a policy

Evaluating arbitrary mathematical expressions is an execution action. While the server describes these as 'deterministic tools', an expression evaluator that accepts arbitrary input could potentially be abused to execute unintended computations (e.g., deeply nested or resource-intensive expressions causing denial of service).

From the tool's definition "Evaluate mathematical expressions" — the tool actively evaluates/executes an expression, not merely retrieves static data. The description says "Use this for ANY math calculation", implying arbitrary expression input.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

calculate Rate-limited

calculate 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": {
    "calculate": {
      "limits": [
        {
          "counter": "calculate_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 Basic, so you can run agents against it safely.

FAQ

Questions about calculate

What does the calculate tool do? +

Evaluate mathematical expressions. Supports standard math operations, functions, and constants. Use this for ANY math calculation. It is categorised as a Execute tool in the Basic MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on calculate? +

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

What risk level is calculate? +

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

Can I rate-limit calculate? +

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

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

calculate is provided by the Basic MCP server (msilverblatt/basic-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.