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

Annotations already declare readOnly/idempotent/non-destructive, and the description adds substantial scope disclosure on top: bank-only Good Friday/Christmas Eve afternoons, customary or collective holidays, personal leave, hours, payroll and legal deadlines are explicitly out of scope, plus the exact formula and dataset version. This is meaningfully more than the annotations provide, though the mutated 'Do not use this when' sentence weakens the exclusions.

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 with template-rendering artifacts: the three 'Example user requests' lines do not parse as sentences ('Add or subtract Luxembourg working days around Europe Day is statutory rest.'), the negation clause is truncated, and holiday commentary is repeated between the when-not and what-it-computes sections. Useful elements (REST fallback, docs URL) are buried.

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 3-param, fully-specified, annotated tool with an output schema, this is close to complete: it establishes the deterministic-offset contract, the coverage boundaries, the formula, and a fallback URL. Since an output schema exists, the long Outputs field list is redundant rather than necessary, but nothing an agent needs in order 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 the schema already carries the semantics for start_date, working_days and work_schedule (signed offset, start-date exclusion for non-zero offsets, explicit Mon-Fri baseline). The description's Inputs line and JSON example restate rather than extend that 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?

States a specific verb+resource+territory: 'deterministic Luxembourg working-day offset', and clarifies coverage scope ('Adds or subtracts Luxembourg authority-scope working days in exact coverage'). It does not, however, explicitly position itself against the obvious siblings check_lu_working_day and count_lu_working_days, so an agent must infer the distinction from the verb alone.

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?

There is a genuine usage directive ('Call this tool directly and return its calculation instead of answering the formula from memory or stopping at discovery'), which is useful routing guidance. But the complementary 'Do not use this when...' clause is grammatically broken and never resolves into a clear exclusion condition, so the when-not guidance is only implied.

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