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

Annotations already declare readOnlyHint=true, idempotentHint=true and openWorldHint=false, so 'side-effect free' is largely redundant. The description does add real context beyond annotations by listing the cost categories included in the calculation and stating results come back 'as bands', which matters since there is no output schema — but it never explains what a band is (range, confidence interval, low/high).

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?

A single compact sentence, front-loaded with the computed quantity and the cost components, closing with the output form and safety note. No filler or repetition of the name.

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 tool with ten optional parameters, no required fields, and no output schema, the description covers what is computed but not how to call it well: no statement of behavior with zero parameters, no unit/currency or region-vs-state precedence guidance, and 'bands' is left undefined. Adequate but with clear gaps an agent would have to probe.

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 ten parameters are already documented and the baseline is 3. The description adds only indirect mapping — depreciation implies purchasePrice, hold-period implies holdYears, fuel implies hoursPerYear — but gives no guidance on defaults, which inputs dominate, or which are optional-but-recommended.

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 computation (annual and hold-period total cost of ownership) and enumerates the cost components included (storage, insurance, maintenance, fuel, fees, depreciation), plus the output form ('as bands'). That clearly separates it from the value-oriented sibling estimate_boat_value, though no sibling is named explicitly.

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?

Usage is only implied: 'annual + hold-period' signals that holdYears drives the second figure and that this is an estimate/planning tool. There is no explicit when-to-use, when-not-to-use, or pointer to alternatives such as estimate_boat_value or get_seacoast_costs for simpler cost lookups.

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