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

Annotations already declare readOnlyHint=true, idempotentHint=true and openWorldHint=false, so the safety profile is covered. The description adds one genuinely useful behavioral detail: data volumes for Switzerland are counted separately and are not deducted from the France volume. It does not say whether the list is exhaustive, ordered, paginated, or how often tariffs change.

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?

Everything sits in a single run-on sentence with a nested parenthetical, which makes it harder to scan than a short lead sentence followed by a bulleted field list. The content is dense but front-loaded with the core purpose, and there is no filler.

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?

Because an output schema exists, most of the description's length is spent re-describing return fields rather than covering what the schema cannot: when to prefer this catalog call over the comparison and recommendation siblings. The separate-Switzerland volume note is the one piece of context the structured data would not supply.

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 zero parameters, so there is no parameter meaning to add; the baseline of 4 applies. The description instead clarifies the shape of the returned data fields, which is useful even though an output schema already exists.

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 ('Liste les forfaits Flytel commercialisés') and enumerates exactly what each entry contains (monthly TTC price, commitment, data volumes, calls, eSIM, network, address). This is far more than a restatement of the title, though it never distinguishes itself from siblings like get_plan, compare_plans or find_best_plan.

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 statement of when to call this rather than compare_plans, find_best_plan, flytel_conseil_forfait or get_plan, nor any precondition or exclusion. The only implicit guidance is that it is a catalog-style listing, which the agent must infer from the name alone.

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