This record as markdown: /tools/io-tinyfn-tinyfn/calculate-stddev.md
What calculate_stddev does on TinyFn
AI agents call calculate_stddev 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 |
|---|---|---|---|
numbers | string | Yes | Comma-separated numbers |
population | boolean | — | Use population std dev vs sample std dev |
Parameters from the server's own tool schema.
Why calculate_stddev is rated Low
This is a mathematical calculation tool that takes numerical inputs and returns a statistical measure. It performs no data modifications, deletions, financial transactions, or external operations. It is deterministic and read-only in nature, consistent with the server's purpose of providing '500+ deterministic tools for AI agents: math, conversion, validation, hashing, encoding, date/time.'
From the tool's definition Tool name 'calculate_stddev' and description 'Calculate standard deviation' indicate a pure computational/statistical function that reads input data and returns a calculated result with no side effects, modifications, or external operations.
Attacks that exploit this kind of access
The rule that runs calculate_stddev 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_stddev, this is the rule to start with:
calculate_stddev 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_stddev call is checked against it from then on.
Questions about calculate_stddev
Calculate standard deviation. It is categorised as a Read tool in the TinyFn MCP Server, which means it retrieves data without modifying state.
calculate_stddev accepts 2 parameters: numbers, population. Required: numbers. 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_stddev: 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_stddev 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_stddev 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_stddev. 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_stddev 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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