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

Beyond the annotations (readOnly, idempotent, non-destructive, openWorld), the description adds material behavioral context: read-only with no key and no cost, that it returns verdicts rather than register data, an itemized list of what the verdicts cover, and an explicit boundary of what it cannot prove (signing authority, bank account ownership, solvency, reliability). No annotation contradiction.

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?

Purpose and pre-action framing are front-loaded, and the return enumeration earns its length because there is no output schema. It is still dense and multi-sentence; the return list and the limitations paragraph could be tightened without losing meaning.

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?

With no output schema, the description carries the full burden of describing returns and does so thoroughly (registration status, name match, VIES validity and name match, sanctions candidates, insolvency case, open questions, check_id). Safety is covered by annotations and the remaining gaps are explicitly disclosed, so an agent has everything needed to call 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 100%, so the baseline is 3, but the description adds real guidance beyond the schema: it instructs the caller to supply the KvK number, company name and EU VAT number exactly as the document states them, which matters for the name-match verdicts. It does not expand on the compatibility-only city field or the purpose field beyond what the schema already says.

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?

States a specific verb and resource (check a Dutch/EU counterparty against official sources) and pins the scope to a pre-action decision point. The description makes clear this is verification of identity/registration status rather than a generic lookup, and it is readily distinguishable from record_counterparty_check and verify_astranl.

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?

Explicit about when to invoke it ('before your own next step, such as onboarding a supplier, paying an invoice or signing an order') and names the follow-up alternative (record_counterparty_check with the check_id when a colleague or auditor must verify later). It also states the negative case: AstraNL does not search the Dutch register by name, so look a number up at kvk.nl.

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