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

Annotations already declare read-only, idempotent, non-destructive and open-world, so the description does not need to restate safety. It adds genuinely non-obvious behavior instead: the x402/API-key cost model, the 5-free-calls-per-day allowance, and the output shape ('one verdict and a cite_as line'). It does not cover failure modes (no match, partial register coverage) or latency, which keeps it below a 5.

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 use case and scope are front-loaded, and the cost/input/output clauses are each doing work for a paid, multi-source tool. It is a single dense paragraph of moderate length with some compression (parenthetical country lists) that borders on information dumping but stays readable.

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?

No output schema exists, and the description compensates by stating the return ('one verdict and a cite_as line') and the sources behind that verdict, along with cost and identifier input. For a zero-required-parameter, open-world paid tool it is close to complete, with only edge-case behavior left unstated.

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 100%, so the schema baseline is 3, but the description adds actionable guidance the schema does not: an identifier (name or id) is what is needed and country should be supplied where possible, which matters because the schema marks zero parameters required. It omits the kvk/vat/domain parameters entirely, so it does not fully mirror 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 names a specific resource and enumerates its full scope: registers in 10 countries plus GLEIF, director/owner/parent sanctions and PEP screening, VAT, Peppol, website, plus financial health and insolvency checks in named countries. That enumeration lets an agent distinguish it from narrower siblings such as eu_vat_check, company_health or company_lookup without opening any schema.

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?

'Use for due diligence before a deal, contract or large payment' gives a clear triggering context, and the payment details tell the agent when a paid call is viable versus free-tier. There is no explicit statement of when not to use it or which narrower sibling to prefer for a single check, so it stops short of a full routing instruction.

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