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

Annotations already declare readOnlyHint, idempotentHint, non-destructive, so safety is covered. The description adds real value beyond that by disclosing the exact deterministic formula and naming the output fields, clarifying that this is a pure computation with no side effects or hidden state.

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, formula front-loaded, output shape and a cross-reference following. No filler words; each clause earns its place.

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 low-complexity, 2-parameter deterministic calculator with a full output schema and rich annotations, the description is nearly sufficient. The one missing element is when-to-use guidance versus sibling calculators, though the formula and discoverability pointer largely compensate.

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 both parameters (co2_g_km, power_kw) are already documented in the schema. The formula references CO2 and P_kW, reinforcing the mapping, but adds no format or constraint detail beyond what the schema provides. Baseline 3 is appropriate.

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 ('French fiscal horsepower CV') and even gives the exact formula '(CO2/45) + (P_kW/40)^1.6', making it unmistakable what this computes. An agent can identify the domain without opening the schema, and the reference to related 'auto-transport' calculators anchors it in context.

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 use this tool versus alternatives. The only pointer is 'See list_bundles for related calculators', which is a discovery hint rather than a usage condition or exclusion. The agent gets no guidance on selecting this over sibling car/tax calculators like calculate_malus_ecologique.

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