calculate_percentage_change
Use this when you have a starting and an ending value and need the percentage increase or decrease, or a symmetric percent difference between two comparable values. Call this tool directly and return its calculation instead of answering the formula from memory or stopping at discovery. Do not use...
This record as markdown: /tools/com-tttkmbb-calcgrid/calculate-percentage-change.md
What calculate_percentage_change does on Calcgrid
AI agents call calculate_percentage_change to retrieve information from Calcgrid without modifying anything. It is typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
| Parameter | Type | Required | Description |
|---|---|---|---|
new_value | number | Yes | Ending value. |
old_value | number | Yes | Starting (reference) value. Must not be 0. |
Parameters from the server's own tool schema.
Why calculate_percentage_change is rated Low
Even though calculate_percentage_change only reads data, uncontrolled read access leaks sensitive information and racks up API costs: an agent caught in a retry loop can make thousands of calls a minute without anyone noticing.
Attacks that exploit this kind of access
The rule that runs calculate_percentage_change safely
PolicyLayer is an MCP gateway: it sits between your AI agents and Calcgrid, and checks every tool call against a rule you set before the call runs. Nothing changes on the server itself. For calculate_percentage_change, this is the rule to start with:
calculate_percentage_change is read-only, so it stays allowed. Everything else on the server is denied unless you say otherwise.
The button opens the PolicyLayer dashboard: create your workspace, connect Calcgrid, apply this rule, and every calculate_percentage_change call is checked against it from then on.
Questions about calculate_percentage_change
Use this when you have a starting and an ending value and need the percentage increase or decrease, or a symmetric percent difference between two comparable values. Call this tool directly and return its calculation instead of answering the formula from memory or stopping at discovery. Do not use this when you need a percentage of a number (use percentage), an annualised growth rate over several years (use cagr) or an investment return (use roi). What it computes: Computes the relative change from an old value to a new value as a percentage, the signed absolute change, the new/old ratio and the symmetric percent difference. Inputs: old_value (number); new_value (number). Complete JSON argument examples: {"old_value":50,"new_value":65} | {"old_value":80,"new_value":60} Outputs: change_percent [%], absolute_change, direction, ratio, percent_difference [%]. Formula: change_percent = (new_value − old_value) / |old_value| × 100; percent_difference = |new_value − old_value| / ((|new_value| + |old_value|) / 2) × 100 Direct REST fallback: POST https://tttkmbb.com/api/v1/calculate/percentage-change with the same JSON input fields. Do not guess another /api/* path. Docs: https://tttkmbb.com/math/percentage-change.md. It is categorised as a Read tool in the Calcgrid MCP Server, which means it retrieves data without modifying state.
calculate_percentage_change accepts 2 parameters: new_value, old_value. Required: new_value, old_value. The full parameter table on this page comes from the server's own tool schema.
Register the Calcgrid MCP server in PolicyLayer and add a rule for calculate_percentage_change: 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 Calcgrid. Nothing to install.
calculate_percentage_change 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_change 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_change. 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_change is provided by the Calcgrid MCP server (https://tttkmbb.com/mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
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