get_vat_rates

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

With no annotations, the description alone must convey behavior. It states it returns 'current' rates and specifies 'standard/reduced', which gives some behavioral context. However, it does not disclose expected behavior for invalid or non-EU codes, error handling, or whether only one rate or both are always returned. Since the output schema exists, some of this may be covered there, but the description could add more behavioral detail.

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?

The description is a single, efficient sentence that front-loads the action and resource. It contains no filler or redundancy, and every word adds value.

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?

For a simple one-parameter lookup tool with an output schema, the description covers the essential purpose, scope, and parameter format. It does not mention edge cases like non-EU territories (e.g., EEA), but the tool is straightforward and the description is adequate for an agent to invoke it correctly.

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 description coverage is 0% for the only parameter (country_code), so the description must supply meaning. It does so by specifying the format ('ISO 3166-1 alpha-2') and the scope ('EU country'), which goes well beyond the bare schema type 'string'. This is sufficient for the single parameter.

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 uses a specific verb ('Get') with a clear resource ('VAT rates') and scopes it to 'EU country' with a defined code format ('ISO 3166-1 alpha-2'). This clearly distinguishes it from sibling tools like validate_vat or lookup_company_by_vat, which are about validation and company lookup, not rate retrieval.

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?

The description clearly situates when to use the tool: when you need current standard and reduced VAT rates for an EU country. It does not explicitly mention alternatives or exclusions, but the context is unambiguous, and sibling tools are semantically distinct enough that no further guidance is strictly needed.

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