Calculates a specified percentage of a given number (e.g., 20% of 150).
AI agents call calculate_percentage_of to retrieve information from Calculator without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This is a stateless arithmetic operation that retrieves a computed result. It matches the 'Read' category definition: retrieves data (the calculated result) with no side effects. The low severity reflects that misuse of a percentage calculator poses no security risk—it cannot modify data, execute code, or cause any harm.
From the tool's definition Tool performs pure mathematical calculation: 'Calculates a specified percentage of a given number'. No state modification, no external effects, no side effects.
Attacks that exploit this kind of access
Calculates a specified percentage of a given number (e.g., 20% of 150). It is categorised as a Read tool in the Calculator MCP Server, which means it retrieves data without modifying state.
Register the Calculator MCP server in PolicyLayer and add a rule for calculate_percentage_of: 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 Calculator. Nothing to install.
calculate_percentage_of is a Read tool with low risk. Read-only tools are generally safe to allow by default.
Yes. Add a rate_limit block to the calculate_percentage_of 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.
Set action: deny in the PolicyLayer policy for calculate_percentage_of. 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.
calculate_percentage_of is provided by the Calculator MCP server (mvavassori/calculator-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Every MCP server has a record like this.
Type a name, get the same breakdown: verified identity, auth posture, risk grade, capabilities, recommended policy.
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