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

No annotations are provided, so the description carries the full burden of behavioral disclosure. It does not state whether this is read-only, whether any external dependency may fail, or what the response looks like. 'Validate' implies a check, but the absence of an output schema means the agent is left guessing about the result payload.

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?

A single clear sentence contains all the essential purpose information with no filler. The EU scope and VIES context are front-loaded.

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?

The tool is simple and both parameters are fully documented, so an agent can construct a correct call. Still, with no output schema and no annotations, the description should at least indicate whether a boolean, VIES status object, or company details are returned; that information is missing.

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%, so the baseline applies: both parameters already have useful descriptions, including stripping the country prefix from vatNumber. The tool description adds no further parameter detail beyond labeling the number as an EU VAT number.

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 ('Validate') and a precise resource ('counterparty's EU VAT number in the VIES system'). It is immediately distinguishable from sibling tools like sprawdz_nip and sprawdz_regon because it names the European Commission VIES system and EU VAT scope.

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 implies the use case: call this tool when an EU VAT number needs VIES validation. However, it never explicitly states when not to use it or points to an alternative, leaving the routing decision to inference from the tool name and sibling list.

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