SmartTools

VAT calculator

vat_calculator

Add VAT to a net amount or remove it from a gross amount. Runs on smart-tools.xyz.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "amount": "<amount>",
      "rate": "<rate>"
    },
    "name": "vat_calculator"
  }
}

Input Schema

Name	Required	Description
`rate`	Yes	VAT rate, percent
`amount`	Yes	The amount
`locale`	No	Language for the source_url link (default en)
`direction`	No	add: amount is net → gross; remove: amount is gross → net (default add)

Schema Changelog

Changes observed during successful MCP inspections.

First observedAug 17, 2026

TDQS

A3.7/5.0

Behavior3/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

There are no annotations, so the description carries the burden. It discloses the two core operations (add/remove) but does not mention output format, rounding behavior, or any other behavioral traits. This is acceptable for a basic calculator but still leaves ambiguity.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness3/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The first sentence is concise and front-loaded with the tool's purpose. However, the second sentence 'Runs on smart-tools.xyz' adds no selection or invocation value, so not every sentence earns its place.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness3/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a simple calculator with full schema coverage and no output schema, the description is minimally adequate. It omits details about return values, rounding, or precision, which could matter for VAT calculations, but the core purpose is clear.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, and the schema already describes each parameter (amount, rate, locale, direction) with enums. The description adds little beyond restating the add/remove semantics found in the 'direction' parameter description, so baseline 3 is appropriate.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description begins with a specific verb+resource: 'Add VAT to a net amount or remove it from a gross amount.' This clearly distinguishes the tool from sibling calculators (e.g., percentage_calculator, discount_calculator) by naming VAT as the resource and both supported directions.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines4/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description provides clear context for when to use the tool: when you need to add VAT to a net amount or remove VAT from a gross amount. It does not explicitly name alternatives or when-not conditions, but the two modes are sufficient guidance for a simple calculator.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

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