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

Annotations already cover safety and openness (readOnlyHint=true, openWorldHint=true), yet the description still adds substantive behavior: two external data sources, quota tiers per call/per day, and how to lift the limit via a free key. It does not explain batch-failure semantics for the up-to-25 identifiers, which is the main remaining gap.

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?

Two sentences: purpose and return contents first, then the usage trigger, then quota and key information. Every clause carries information an agent needs, and nothing is repeated from the schema or annotations.

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?

For a single-parameter, read-only, no-output-schema tool, the description covers purpose, trigger, data sources, and quota constraints. Return-value shape is unnecessary given the enumerated checks, and error-code interpretation is plausibly delegated to the sibling expliquer_code_rejet.

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% and the schema already states that SIREN or SIRET strings are accepted with spaces and dots tolerated. The description adds digit-length semantics (9 for SIREN, 14 for SIRET) and confirms plural input, which the schema does not state, so it earns a step above the baseline 3.

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 verb and resource (verifying SIREN/SIRET against the official registry and VIES) and enumerates exactly what is returned: existence, active/ceased status, name, address, and VAT validity. It is clear on its own, but it never distinguishes itself from the sibling verifier_tva, which overlaps on the VAT-validity check.

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 an explicit triggering context ('À utiliser avant de payer une facture ou de créer un client'), which is real decision guidance rather than generic filler. It stops short of naming alternatives or exclusions, so nothing tells the agent when to prefer verifier_tva or valider_facture over this tool.

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