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

Annotations already declare readOnly/idempotent/non-destructive, so the safety profile is covered; the description goes further with substantive behavioral rules – no private-employer adoption is inferred for Cabinet Order 330, Section 2 observances add no rest, shortening is conditional rather than full-day, and it warns against guessing another /api/* path. These are genuine additions beyond the annotations.

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 opening usage rules are front-loaded and useful, but the text is unusually dense and repetitive – the requirement for explicit calendar_basis/work_schedule is stated three separate times, and the outputs list is dumped verbatim despite an output schema existing. Information value is high but wording is bloated.

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 complex, policy-heavy calculator it supplies the required context: inputs, enumerations, a formula, REST fallback endpoint, and docs link, and an output schema exists so return values need not be explained. Nothing essential for correct 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%, so the schema already documents every parameter, including the calendar_basis and work_schedule enums and their selection conditions. The description largely restates those same requirements rather than adding new syntax or format meaning, so the baseline of 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 states a specific verb+resource (count Latvia working days) and clarifies the authoritative scope: 'Counts authority-scope working and non-working dates in a range,' explicitly required calendar_basis and work_schedule, and what it will not cover (six-day rosters, other religious calendars, payroll). It is clearly distinguishable from the country-agnostic siblings, though it never names its closest relatives (e.g. check_lv_working_day, add_lv_working_days) to sharpen the boundary.

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 'Use this when...' and 'Do not use this when...' framing, mandates calendar_basis and work_schedule=mon_fri_planning, and enumerates excluded cases (six-day/shift rosters, bank/exchange openings, legal deadlines). What it lacks is direct routing to sibling alternatives rather than a generic 'do not use' list.

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