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

Annotations already declare readOnlyHint, idempotentHint, non-destructive and closed-world, so the safety profile is covered. The description adds genuine context beyond them by disclosing the data vintage (30 June 2026) and that responses carry sources and limitations. It says nothing about error behavior for invalid department codes, but that is a minor gap given the annotation coverage.

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?

A single compact sentence with zero filler, and the most decision-relevant facts (subject, geography, date, caveats) are packed up front. It is arguably too terse for an agent needing usage routing, but nothing is wasted.

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 lookup with full schema coverage, full annotations, and no output schema, the description covers subject, geographic granularity, data vintage, and the presence of sources/limitations. The only missing element an agent would want is guidance on when to prefer compare_departments.

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 description coverage is 100% and the single 'code' parameter is fully documented in the schema, including metropolitan format examples such as 01, 75, 2A. The description only implies that 'par département' corresponds to that parameter and adds no new syntax or validation meaning, so the baseline 3 applies.

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 resource: Arcep 4G/5G coverage counts broken down by department, dated 30 June 2026. It is a noun phrase with no explicit verb, but the resource plus the 'par département' scope makes clear it returns per-department data, which distinguishes it from compare_departments (comparison) and list_datasets (catalog).

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?

There is no when-to-use guidance and no mention of the sibling tools. An agent must infer on its own that this is the single-department lookup and that compare_departments is the multi-department alternative.

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