This record as markdown: /tools/io-tinyfn-tinyfn/compound-interest.md
What compound_interest does on TinyFn
AI agents call compound_interest 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 |
|---|---|---|---|
rate | number | Yes | Annual interest rate (as percentage, e.g., 5 for 5%) |
time | number | Yes | Time in years |
principal | number | Yes | Initial principal |
compounds_per_year | integer | — | Compounding frequency per year |
Parameters from the server's own tool schema.
Why compound_interest is rated Low
This is a deterministic mathematical utility that retrieves or derives a computed value without side effects. While the result may inform financial decisions, the tool itself does not move money, create financial obligations, or execute external operations. It is purely computational, fitting the Read category.
From the tool's definition Tool name 'compound_interest' and description 'Calculate compound interest' indicate a mathematical calculation function.
Attacks that exploit this kind of access
The rule that runs compound_interest 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 compound_interest, this is the rule to start with:
compound_interest 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 compound_interest call is checked against it from then on.
Questions about compound_interest
Calculate compound interest. It is categorised as a Read tool in the TinyFn MCP Server, which means it retrieves data without modifying state.
compound_interest accepts 4 parameters: rate, time, principal, compounds_per_year. Required: rate, time, principal. 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 compound_interest: 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.
compound_interest 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 compound_interest 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 compound_interest. 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.
compound_interest 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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