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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so the safety profile is covered. The description adds genuine value beyond that by disclosing the return contents (coverage, denominators, city page URL) and warning that the figures are partial counts, not market share or a full census.

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?

Three tight sentences: what it counts, what it returns, what it is not. The caveat is front-loaded with the core action rather than buried, and each sentence carries information an agent would otherwise guess wrong.

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?

An output schema exists, so return values need no explanation, and annotations carry the safety profile. Still missing are the input format for city and any routing guidance relative to resolve_city, which for a city-keyed lookup tool are the two gaps an agent is most likely to hit.

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 single 'city' parameter has 0% schema description coverage, so the description must compensate. It hints that arrondissements are folded in for Paris/Lyon/Marseille but never states the expected input form (plain name vs. arrondissement code vs. a resolve_city slug), leaving the one thing the agent must get right underspecified.

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: counting Ilicompta-indexed listings per city, with explicit handling of arrondissements for Paris, Lyon and Marseille. An agent can tell this apart from search_cabinets or find_accountants, though the description does not name those siblings to draw the contrast.

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 clarifies what the data is not (market share, exhaustive census), which prevents misreading, but gives no positive guidance on when to call this versus resolve_city or search_cabinets. Usage is only implied by the counting scope.

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