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

With no annotations provided, the description fully discloses behavior: Luhn checksum, SIRENE registry check, VAT number computation and VIES validation, return verdicts (ready/not_ready/check_vat_manually), VIES flakiness handling, 1h cache, and price. No contradictions.

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 description is a single paragraph that is dense but not wasteful. It front-loads the purpose and includes all key details without unnecessary elaboration.

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?

Given no output schema, the description explains the three possible return values (ready/not_ready/check_vat_manually) and additional context (caching, pricing). For a single-parameter tool, this provides complete understanding of behavior and output.

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?

The schema has one parameter 'number' with 0% description coverage. The description compensates by explaining that the parameter accepts a SIREN or SIRET number, providing explicit examples with query format. This adds significant meaning beyond 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 clearly states it's a 'one-call compliance check for French e-invoicing reform' and enumerates the specific checks performed (Luhn, SIRENE, VIES). While it does not explicitly differentiate from sibling tools like validate_siret_fr or validate_vat_eu, the combined nature of the check makes its purpose distinct and clear.

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?

The description implies usage for comprehensive French e-invoicing compliance but does not explicitly state when to use this tool versus alternatives. It provides query format and pricing, but lacks guidance on exclusions or specific scenarios.

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