This record as markdown: /tools/io-tinyfn-tinyfn/loan-payment.md
What loan_payment does on TinyFn
AI agents call loan_payment 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 (percentage) |
months | integer | Yes | Loan term in months |
principal | number | Yes | Loan amount |
Parameters from the server's own tool schema.
Why loan_payment is rated Low
This tool performs a deterministic mathematical calculation (loan payment formula) based on input parameters. It retrieves or computes a result without creating, modifying, deleting, or executing any external operations or state changes. It does not move money, commit financial obligations, or perform any write/execute/destructive operations.
From the tool's definition Tool name is 'loan_payment' and description states 'Calculate monthly loan payment' — a pure calculation/retrieval of derived financial data with no side effects on accounts, balances, or systems.
Attacks that exploit this kind of access
The rule that runs loan_payment 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 loan_payment, this is the rule to start with:
loan_payment 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 loan_payment call is checked against it from then on.
Questions about loan_payment
Calculate monthly loan payment. It is categorised as a Read tool in the TinyFn MCP Server, which means it retrieves data without modifying state.
loan_payment accepts 3 parameters: rate, months, principal. Required: rate, months, 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 loan_payment: 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.
loan_payment 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 loan_payment 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 loan_payment. 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.
loan_payment 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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