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

No annotations are provided, so the description carries the full burden. It does disclose a genuine behavioral constraint (the 100-number batch cap), but says nothing about partial failures, per-item error handling, rate limits, or what the 'requester' value is used for.

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 sentence with the verb and batch limit front-loaded, followed by parenthetical use cases; no filler. It is tight, though the terseness leaves obvious gaps unaddressed.

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?

An output schema exists, so return values need not be described. Still, for a 0%-coverage, annotation-free tool, the description omits VAT number format expectations, partial-failure semantics, and the meaning of 'requester' — leaving the agent guessing on real call-shaping details.

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%, so the description must compensate and largely does not. It implies the 'vats' array holds EU VAT numbers and caps the count at 100, but gives no expected format (country prefix, separators), and the 'requester' parameter — with a surprising default of HU33119856 — is completely unexplained.

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 states a specific verb and resource ('Verify ... EU VAT numbers') and adds batch scope ('up to 100 ... at once'), which implicitly separates it from the single-number sibling verify_vat. It does not explicitly name verify_vat or verify_eori_batch as the alternatives, so the differentiation is inferred rather than stated.

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?

It lists business contexts (supplier/customer onboarding, KYB, invoice checks), which implies when the tool is relevant. However, it never says when to prefer this over verify_vat for a single number, or when verify_eori_batch is the right call instead — no exclusions or routing guidance.

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