This record as markdown: /tools/io-tinyfn-tinyfn/mortgage-calculator.md
What mortgage_calculator does on TinyFn
AI agents call mortgage_calculator 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) |
years | integer | — | Loan term in years |
home_price | number | Yes | Home price |
down_payment | number | — | Down payment |
Parameters from the server's own tool schema.
Why mortgage_calculator is rated Low
This tool performs mathematical calculations on mortgage parameters (principal, interest rate, term, etc.) to return computed values like payment amounts or amortization schedules. It is deterministic computation with no side effects—no data is created, modified, deleted, or financial transactions initiated. The operation is read-like: it takes inputs and returns calculated results.
From the tool's definition Tool name 'mortgage_calculator' and description 'Calculate mortgage details' indicate a calculation/query operation that retrieves or computes mortgage information based on input parameters without modifying any data or triggering financial transactions.
Attacks that exploit this kind of access
The rule that runs mortgage_calculator 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 mortgage_calculator, this is the rule to start with:
mortgage_calculator 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 mortgage_calculator call is checked against it from then on.
Questions about mortgage_calculator
Calculate mortgage details. It is categorised as a Read tool in the TinyFn MCP Server, which means it retrieves data without modifying state.
mortgage_calculator accepts 4 parameters: rate, years, home_price, down_payment. Required: rate, home_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 mortgage_calculator: 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.
mortgage_calculator 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 mortgage_calculator 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 mortgage_calculator. 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.
mortgage_calculator 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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