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

Beyond the readOnlyHint/openWorldHint annotations, it discloses that the check is live, that name_matches is a consistency signal and explicitly not proof of ownership, and that vies.status 'unavailable' is an indeterminate result rather than an invalid one. These are exactly the behavioral caveats an agent needs to avoid misreporting results.

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 verb and scope are front-loaded and every sentence carries information, with no filler or restatement of the title. Sentences are long and parenthetically dense, which slightly hurts scannability.

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 return-value burden and does so: it enumerates returned fields (name, address, company active, insolvency proceeding, name_matches, vies.status). An agent has enough to call the tool and interpret its result without further documentation.

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 is 3, but the description adds real meaning: requester_vat is explained as producing a consultation number that serves as proof of the check, not merely a lookup input. The accepted input forms (FR VAT, SIREN, SIRET) are already in 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 states a specific verb and resource: a live validity check of a French VAT number (or SIREN/SIRET VAT number) against VIES, crossed with the French registry. This is functionally distinct from siblings like get_company or validate_identifier, but no sibling is named, so it falls short of explicit differentiation.

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 gives clear operative guidance: pass requester_vat to obtain a VIES consultation number as proof, compare returned names to confirm ownership, and retry later when vies.status is 'unavailable'. It does not name or exclude any sibling tool, but the conditions for correct use are well covered.

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