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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and a closed-world scope, so the safety profile is fully covered elsewhere. The description adds only the domain restriction to metropolitan departments; it says nothing about what the comparison returns, whether results are ordered, or how counts are aggregated — context that matters since there is no output schema.

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?

One sentence, front-loaded with the verb and carrying the scope constraint immediately. There is no filler or redundancy.

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 one-parameter read-only tool with rich annotations, the definition is broadly sufficient to call it correctly. The remaining gap is the return shape: with no output schema, the description should at least indicate that the result is a per-department comparison of 4G/5G site counts.

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?

There is a single parameter and the schema's item description already gives code examples and the 'métropolitain' qualifier. The description reinforces that the codes are metropolitan departments and that the accepted cardinality is 2 to 5, which is mildly useful, but it adds no format or validation detail 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 names a specific verb ('Compare') and a specific resource ('comptages de sites 4G/5G') scoped to '2 à 5 départements métropolitains', so the operation is unambiguous. It does not, however, distinguish itself from sibling tools such as get_department_5g, which an agent might reasonably consider for a single department.

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?

Usage is only implied by the verb: an agent can infer it should be used when comparing several departments rather than fetching one. There is no explicit statement of when not to use it, no mention of the single-department alternative, and the 2–5 range it states is already enforced by the schema's minItems/maxItems.

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