This record as markdown: /tools/io-tinyfn-tinyfn/calculate-margin.md
What calculate_margin does on TinyFn
AI agents call calculate_margin to retrieve information from TinyFn 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 |
|---|---|---|---|
cost | number | Yes | Cost price |
selling_price | number | Yes | Selling price |
Parameters from the server's own tool schema.
Why calculate_margin is rated Low
This is a pure calculation tool that performs a deterministic mathematical operation (profit margin = (profit / revenue) × 100 or similar formula). It retrieves no external data, creates no records, executes no arbitrary code, and causes no side effects. It falls squarely in the Read category as a computation-based query.
From the tool's definition Tool name 'calculate_margin' and description 'Calculate profit margin' indicate a mathematical calculation operation that reads input values and returns a computed result without modifying any data.
Attacks that exploit this kind of access
The rule that runs calculate_margin safely
PolicyLayer is an MCP gateway: it sits between your AI agents and TinyFn, and checks every tool call against a rule you set before the call runs. Nothing changes on the server itself. For calculate_margin, this is the rule to start with:
calculate_margin 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 TinyFn, apply this rule, and every calculate_margin call is checked against it from then on.
Questions about calculate_margin
Calculate profit margin. It is categorised as a Read tool in the TinyFn MCP Server, which means it retrieves data without modifying state.
calculate_margin accepts 2 parameters: cost, selling_price. Required: cost, selling_price. The full parameter table on this page comes from the server's own tool schema.
Register the TinyFn MCP server in PolicyLayer and add a rule for calculate_margin: 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 TinyFn. Nothing to install.
calculate_margin 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_margin 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_margin. 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_margin is provided by the TinyFn MCP server (https://api.tinyfn.io/mcp/all/). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
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