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

Annotations already declare readOnlyHint=true and destructiveHint=false, so the safety profile is covered. The description adds genuinely useful behavior beyond that: what the totals include (statutory employer charges, excluding EoR fees), how monthly salaries trigger the statutory 13th/14th month, row ordering, and a data snapshot date. However, with an output schema present and annotations covering safety, these additions are helpful context rather than filling a disclosure gap, so a 3 is warranted.

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?

Front-loaded with the 'Use this when' trigger and the exclusion, which is the right ordering. It is somewhat long and repeats the monthly-salary point twice with two long parenthetical examples, a small amount of redundancy for an otherwise tight single paragraph.

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?

Given an output schema exists, the description need not explain return values, yet it still sketches them (totals, ratio to smallest, contribution ceilings) which only helps. For a read-only comparison tool with a fully documented schema, nothing an agent needs to call it correctly 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%, so every nested field (salary, country, salary_period, salary_currency, payments_per_year) is already documented in the schema. The description reinforces the monthly case and gives currency examples ('240,000 PLN'), but adds no semantics the schema does not already carry. 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?

The description names a specific operation (compute total employer cost) over a specific input (2-6 country/salary offers) and immediately names the sibling it is not: 'Do not use when the salary is the same in every country (use compare_countries)'. An agent can distinguish it from compare_countries, compare_structures or employer_cost without opening a 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?

It gives explicit entry conditions (multiple offers in 2-6 countries, each with its own gross salary), an explicit exclusion plus the alternative tool to use instead, and two worked natural-language examples including one in French. Nothing about selection is left to inference.

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