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

Annotations already declare readOnly/idempotent/non-destructive, so the safety bar is covered. The description adds real value beyond that: the deterministic nature, the exact formula, the 2026-2027 dataset window, the output field list, and a REST fallback endpoint. It does not flag rate limits or auth needs, but for a pure calculator that is minor.

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?

Well front-loaded, with the when-to-use condition leading and supporting detail (formula, outputs, fallback) following. It is somewhat padded with output field enumeration and a REST fallback line, and contains a duplicated 'Italy Italy' typo, but nothing is egregiously wasteful.

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?

An output schema exists so return values need not be described, and annotations cover the safety profile. The description still supplies scope, exclusions, formula, and dataset window, leaving an agent able to call it correctly. Only minor gaps (no explicit note on invalid/out-of-range dates) remain.

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 there is only one parameter ('date', Gregorian date in Italy coverage). The description restates 'Inputs: date (date)' and gives JSON examples but adds no semantics beyond what the schema already documents, 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?

States a specific verb+resource: it 'Checks a date against the Saturday-Sunday weekend baseline and exact 2026-2027 authority events' for Italy. The country scope makes it clearly distinguishable from the many check_*_working_day siblings without opening any 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?

Provides explicit 'Use this when' and 'Do not use this when' sections that name the excluded cases (regional, municipal, local patron-saint, school, bank, sector, employer-specific schedules). The exclusion sentence is grammatically garbled ('...are not inferred'), which slightly blunts the otherwise clear when-to-use guidance.

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