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

With no annotations, the description carries the full behavioral burden. It usefully states that results are 'deterministic' and sourced from statutory FuelEU Maritime Annex II default tables, but it does not explicitly confirm read-only behavior, authentication needs, rate limits, or the response structure.

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?

The definition is a single front-loaded sentence with no wasted words. It names the metric families and data source directly, and is appropriately sized for a simple one-parameter lookup.

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 simple reference lookup with one fully documented parameter and no output schema, the description gives enough context: the metric types returned and the statutory data source. It could still mention units or response shape, but nothing essential to invocation is missing.

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 the single fuel_type parameter is already well documented with an enum and regulatory reference. The description adds no parameter-specific meaning beyond what the schema provides, so the 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?

The description gives a specific verb ('Returns') and resource ('statutory WtW, WtT, TtW, and LCV metrics from FuelEU Maritime Annex II default tables'), so the agent knows exactly what data is retrieved. It does not explicitly differentiate from the sibling calculation tools, but the lookup-versus-calculate distinction is implicit.

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 implied: the tool returns statutory default-table emission factors, so an agent would infer it is used for reference values rather than voyage-specific calculations. No explicit when-to-use guidance, alternatives, or exclusions are provided, so it remains only minimally adequate.

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