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

Annotations already declare readOnly, idempotent and non-destructive behavior, so the safety profile is covered. The description adds useful context beyond that: the applicable jurisdiction/year (2026 France), the input basis (CO2 g/km) and the returned fields, which an agent would not otherwise know.

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?

Two tight sentences, front-loaded with the core purpose, followed by output shape and a cross-reference. Nothing redundant, though the bundle pointer is of marginal value.

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?

For a single-parameter, fully annotated, idempotent calculation with an output schema, the description covers jurisdiction, basis and returned keys. The main omission is eligibility/prerequisite context (e.g. what vehicle classes or thresholds apply), but that is minor given the strong structural coverage.

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% and there is a single required, well-described number field, so the schema carries the semantics. The description only loosely reinforces the CO2/g-km meaning and adds no units nuance beyond the schema. 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 verb and resource ('French ecological malus 2026 ... tax on new vehicle registration'), including the precise domain (CO2 g/km based) and year. An agent can distinguish it from the many other tax/vehicle calculators without opening the 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?

The only guidance is 'See list_bundles for related auto-transport calculators,' which is a navigation pointer, not a when-to-use rule. It never states when this tool should be selected over alternatives like calculate_puissance_fiscale or other vehicle-tax calculators, nor any prerequisites.

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