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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world). The description adds genuinely useful behavior beyond them: results are ordered cheapest-to-most-expensive and an empty list is returned when nothing matches. It stops short of other traits (result caps, filtering strictness), so not a 5.

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-loads the purpose, then criteria, then ordering/empty behavior, then usage routing, ending with a source link. Dense but single-paragraph and every clause carries information; the run-on colon/semicolon structure slightly hurts readability.

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 (returns need not be described) and 100% parameter coverage, the description supplies what structured fields cannot: the sort order, the empty-result semantics, and the routing rule against recommend_plan. An agent has everything needed to call it correctly.

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%, so the schema already documents all three parameters with units (Go, EUR HT per line/month). The description only restates the same criteria (data volume, budget, 5G) without adding syntax, defaults, or interaction rules, so the baseline 3 is correct.

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 verb+resource (search plans/forfaits) plus the exact criteria domain: minimum data volume in France, max monthly budget per line, 5G. It explicitly differentiates itself from the sibling recommend_plan, so an agent can route between them without opening either schema.

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?

"À utiliser quand l'utilisateur donne un besoin chiffré ; sinon préférer recommend_plan" gives both the when-to-use condition and the named alternative, with the selecting condition (numeric need present or absent). 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.