AI agents call calculate_vat to retrieve information from TinyFn without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
| Parameter | Type | Required | Description |
|---|---|---|---|
amount | number | Yes | Amount |
vat_rate | number | — | VAT rate percentage |
inclusive | boolean | — | Is amount VAT inclusive? |
Parameters from the server's own tool schema.
This tool performs a read-only mathematical calculation (VAT computation) with no side effects, no financial transactions, no data modification, and no external operations. It is consistent with the server's stated purpose of deterministic math and conversion tools.
From the tool's definition Calculate VAT (Value Added Tax) — performs a deterministic tax computation; server described as '500+ deterministic tools' for math/conversion
Attacks that exploit this kind of access
Calculate VAT (Value Added Tax). It is categorised as a Read tool in the TinyFn MCP Server, which means it retrieves data without modifying state.
calculate_vat accepts 3 parameters: amount, vat_rate, inclusive. Required: amount. 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_vat: 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_vat 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_vat 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_vat. 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_vat 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.
calculate_vat is one line of TinyFn's registry record.
The record carries the whole server: verified identity, auth posture, risk grade, every tool classified, recommended policy — re-checked continuously.
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