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

With no annotations, the description carries the full burden, and it does disclose genuinely useful behavior: the Annex IV formula and the EUR 2,400/tonne VLSFO-equivalent reference rate. However, it omits the effect of consecutive_non_compliant_years (a statutory penalty multiplier), how voyage_scope affects the applied share, and whether an api_key is required, which are material for correct invocation.

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 tightly packed sentences that lead with the outputs and then the governing formula. The second sentence restates the rate already embedded in the formula, which is mild redundancy, but there is no filler.

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 5-parameter tool with zero annotation coverage, zero schema description coverage, and no output schema, the description is not complete. An agent cannot determine parameter semantics, the non-compliance multiplier behavior, or the auth requirement from this text alone.

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 0% across 5 parameters, so the description must compensate and largely does not. It references 'deficit_gCO2eq' and 'actual_intensity', which are not even schema parameters, while leaving fuel_type, fuel_mass_metric_tonnes, voyage_scope, consecutive_non_compliant_years, and api_key completely unexplained.

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 names a specific verb (calculates) and three concrete outputs: FuelEU Maritime compliance balance, GHG intensity deficit, and statutory cash penalties. That is clearly distinct from siblings like calculate_fueleu_banking_borrowing or calculate_maritime_ets_surrender, though it never explicitly routes the agent away from them.

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 when-to-use, when-not-to-use, or alternative-tool guidance. The agent must infer from the tool name alone whether this is the right penalty tool versus the ETS surrender or banking/borrowing calculators.

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