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

Annotations already declare read-only, idempotent, non-destructive, closed-world, and the description still adds real behavior: result size (30-70 stores per sector), rank tie-breaking via ex_aequo then alphabetical, staleness flags (dernier_test, test_ancien), pagination via page, and the exact failure mode for an unknown sector. That is disclosure well beyond structured fields.

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?

Front-loaded with purpose and alternatives before the return-field dump; every sentence is functional. The long comma-separated field and sector lists are informative but dense, costing a little readability rather than adding waste.

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 contract and does so fully: top-level keys (secteur, marchands), per-item fields, ordering, tie-breaking, and error behavior. Nothing an agent needs to call or interpret this correctly is missing.

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 both params have enums with their own descriptions, so the baseline is 3. The description still adds value by enumerating the ten valid sectors inline and specifying the unknown-sector error, whereas the langue param is only handled by 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?

States a specific verb and resource ('Ranking of ALL tested French online stores in one sector, best score first') and immediately contrasts with the sibling tools trouver_marchands and consulter_marchand by name. An agent can pick this over its four siblings 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?

Explicit trigger ('when the user wants the best stores of a sector as a whole'), a concrete example, and two named alternatives with the condition that selects them (proven-fact filtering -> trouver_marchands, single-store detail -> consulter_marchand). Nothing left to inference.

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