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

Annotations already declare readOnly/idempotent/non-destructive/short-of-open-world, so the bar is lower, yet the description adds substantial scope disclosure: no compensatory dates, no bank-only Good Friday/Christmas Eve, no personal roster, payroll, or legal-deadline computation, plus a formula and dataset scope. The exclusion list is the most valuable content here, though the garbled fragments weaken it.

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 definition is bloated and disorganized: it enumerates 24 output fields already covered by the output schema, embeds a REST fallback and docs URL, and contains malformed fragments such as 'Count Luxembourg working days around Europe Day is statutory rest.' Front-loading is decent, but much of the text does not earn its place.

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 return-value enumeration is unnecessary, and the description covers computation scope and caveats reasonably well. The main gap is that the count-vs-check-vs-add distinction among Luxembourg siblings is left to inference, and the broken exclusion sentence leaves the usage boundary incomplete.

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 coverage is 100%, so the schema already documents all five parameters. The description restates the inputs and emphasizes that mon_fri_planning is 'required explicit,' but adds no syntax or format detail beyond the schema, which sets the baseline at 3.

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 and resource: 'auditable Luxembourg working-day count,' and 'What it computes: Counts authority-scope working and non-working dates in a range.' It is clearly a count-in-range tool, distinct from a single-day check, though it never names sibling tools like check_lu_working_day or add_lu_working_days explicitly.

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 attempts explicit routing with 'Use this when...' and 'Call this tool directly... instead of answering from memory or stopping at discovery,' which is genuinely useful. However, the 'Do not use this when...' sentence is garbled into an incoherent fragment ('Do not use this when luxembourg 2026-2028 statutory holiday dates over an explicitly selected Monday-Friday planning baseline'), so the exclusion guidance fails to communicate.

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