Get VAT rates for a country

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

With no annotations, the description carries the full burden. It discloses the tool is free and requires no API key, implying a read-only operation. It details the output content. It does not mention error handling or rate limits, but the level of detail is adequate for a simple tool.

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

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

Three well-structured sentences. The first sentence lists what is returned, the second explains input format and coverage, and the third states usage trigger and free nature. No redundancy.

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

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

Given a simple tool with one parameter and no output schema, the description covers usage, input semantics, output content, and a behavioral note. Missing error handling or details on response format, but overall complete for typical agent invocation.

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

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

Schema coverage is 100% with a clear description of the parameter. The tool description adds context by specifying the set of valid countries (European jurisdictions) and the format expectations, going beyond the schema.

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

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

The description clearly states the tool returns standard, reduced, super-reduced, and parking VAT rates along with VAT number format and regex for a single European country. It specifies the input format (ISO 3166-1 alpha-2). It distinguishes from sibling tools by focusing on a single country's full rate set, unlike list_eu_vat_rates which likely lists all countries, or check_vat_format which checks format validity.

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

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

Explicitly says 'Use when the user asks "what is the VAT rate in X" or needs the VAT number format for a country.' It also notes coverage of non-EU European jurisdictions. While it doesn't explicitly list when not to use or alternatives, the guidance is sufficient for common use cases.

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