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

Annotations already cover read-only, idempotent, non-destructive, closed-world behavior, so the bar is lower. The description adds real value beyond that: it discloses the formula, the holiday categories excluded from rest (memorial days, person-specific religious rights), and non-computed domains (payroll, legal deadlines, future years).

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?

Labeled sections (What it computes, Inputs, Outputs, Formula, fallback, Docs) give useful structure, but the text is repetitive and garbled ('Croatia Croatia', '2026-2026') and restates exclusions more than once. Appropriate length is undermined by redundancy.

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 explained, yet the description still covers scope boundaries, formula, and a REST fallback endpoint path. For a narrowly-scoped single-date check this is nearly complete, with only the confusing 'Do not use' clause as a gap.

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 both 'date' and 'work_schedule'. The description largely repeats this ('Requires explicit mon_fri_planning') and adds JSON examples, but contributes little semantic meaning beyond the schema's own enum explanation.

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 and resource ('Checks a date against the Saturday-Sunday weekend baseline and exact 2026-2026 authority events') and scopes it to Croatia 2026 article-1 general holidays. An agent can distinguish it from the many sibling check_*_working_day tools by country and year. The garbled opening ('deterministic Croatia Croatia 2026 article 1 general holiday facts') slightly muddies it.

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?

Explicitly instructs 'Call this tool directly and return its calculation instead of answering the formula from memory or stopping at discovery', which is clear usage direction. A 'Do not use this when...' clause exists but is garbled and hard to parse, so exclusions are less actionable than the positive guidance.

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