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

With no annotations, the description carries the transparency burden and discloses a cost (1 credit) and authentication requirement (API key), which are important behavioral traits. It does not mention response format or rate limits, but for a simple lookup tool this is adequate.

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, front-loaded sentence that immediately states the tool's purpose, then adds cost and auth details. Every word earns its place with 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?

For a simple tool with one parameter and no output schema, the description covers purpose, scope (EU countries), and access requirements (credit, API key). It does not describe the return structure, but the term 'VAT rates' gives sufficient context.

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?

The schema defines the parameter 'country' with a pattern for two uppercase letters, but the description adds no additional meaning or usage detail beyond that. Since schema coverage is 0%, the description does not compensate, yet the single parameter is well-specified in the schema itself.

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 retrieves standard and reduced VAT rates for an EU country, with the data source (EU TEDB). This specific verb+resource combination distinguishes it from sibling tools like get_fx_rate or get_holidays.

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 indicates the tool applies to EU countries and mentions a cost of 1 credit and API key requirement, giving clear operational context. It does not explicitly list exclusions or compare against alternatives, but the domain (VAT) is distinct from siblings.

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