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 real behavioural detail beyond that: accent/case-insensitive matching, the possibility that one country returns several zones, and an explicit 'inconnu' status when nothing matches. It does not state how many zones are returned at most or whether matches are ranked.

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 purpose is front-loaded, but the body is one dense run-on sentence with stacked parentheticals describing payload contents that the output schema already defines. The enumerated basin list earns its place; the detailed recital of calls/SMS/MMS/Europe-envelope coverage is largely redundant with the output schema.

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 annotations, a fully documented single parameter, and an output schema, the description covers everything needed to invoke the tool correctly: input forms, fuzzy matching, unknown-result handling, multi-zone results, and the source URL. The remaining gap is the lack of explicit routing guidance relative to the cross-border rule and roaming allowance siblings.

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%, so the baseline is 3, but the description genuinely extends the schema by spelling out the full list of ten basins (genevois, arc-jurassien, bale-mulhouse … monaco) that the schema only implies with an ellipsis. It also states the matching tolerance for the query parameter, which the schema does not mention.

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 opens with a specific verb-and-resource statement: it returns a border zone derived from a basin, city, or neighbouring country, and then enumerates the payload (villes des deux côtés, pays voisins, indicatifs, tarification). It explicitly names the sibling to use for other countries (get_country_info), so the agent can distinguish it from at least one overlapping tool.

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 gives a clear usage context (acceptable query types, fuzzy accent/case tolerance) and an explicit fallback: statut « inconnu » plus a redirect to get_country_info for non-neighbouring countries. It does not clarify its boundary with siblings such as get_cross_border_rule or get_roaming_allowance, even though it returns 'la règle d'usage courte' and Europe-envelope budget data that those tools may also cover.

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