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

Annotations already cover the safe-read profile (readOnlyHint, idempotentHint, openWorldHint=false), but the description adds genuinely useful behavior: what happens with an unlisted destination ('Statut « inconnu »'), plus a source URL for verification. It does not cover rate limits or response shape, but that is largely handled by the 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?

Four compact clauses, each earning its place: purpose, usage routing, unknown-status edge case, and source. Front-loaded with the core capability before the disambiguation.

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 an output schema present, return structure need not be explained; the description still covers routing, the unknown-destination outcome, and provenance. A minor gap is that it does not say whether the destination match is fuzzy or exact, which matters given free-text input.

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 the single parameter is fully documented (type, length bounds, accepted French names or identifiers). The description adds no syntax or lookup detail beyond what the schema already provides, 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?

States a specific resource (the roaming zone of a country/territory and its inclusion in Comontel plans) with a clear retrieval verb. It is immediately distinguishable from the sibling get_roaming_allowance, which the description names.

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?

Gives an explicit when-to-use ('mon forfait marche-t-il en … ?' without a specific plan) and an explicit alternative with its selecting condition ('avec un forfait, préférer get_roaming_allowance'). Nothing is left to inference.

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