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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false and openWorldHint=false, so the safety profile is fully covered. The description adds useful scope info (all three plans at once, no parameters) and discloses returned attributes (subscription_open, availability, how_to_subscribe), but no auth, rate-limit or caching behavior. Adds some value over annotations, not rich.

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?

Front-loaded with the resource and its contents, then usage guidance, then field disclosure. Dense but each sentence carries distinct information; the parenthetical field list is slightly heavy but justified for output attribute naming.

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 not be explained, and the zero-parameter schema is trivial. The description covers resource, scope, routing and source URL, leaving only sibling differentiation (vs get_plan/compare_plans) unstated.

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 tool takes no parameters, so the baseline is 4; the description explicitly confirms 'Aucun paramètre', which matches the empty schema and removes any doubt about hidden filtering options.

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 the specific resource (les trois forfaits mobiles pro Comontel: Essentiel, Pro, Business) and enumerates the content dimensions (prix HT/TTC, Go France/Europe, 5G, réseau, sans engagement). It is clear what the tool returns, though it never explicitly contrasts itself with the sibling get_plan (singular), leaving the plural/singular distinction to inference.

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 states an explicit routing rule: 'À utiliser en premier pour toute question de prix ou de contenu des forfaits.' That tells the agent when to reach for this tool, but it names no alternative and gives no when-not guidance (e.g. when to prefer get_plan or compare_plans).

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