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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world), so the description earns credit by adding policy detail beyond them: seven named state holidays are not work-free, no extra Monday or bridge day is invented, and the planning formula is stated. It also discloses the direct REST fallback path and warns not to guess other /api/* paths.

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 use-when/when-not framing is correctly front-loaded, but the body is padded: the 'Adds or subtracts ... sledenija coverage. Requires explicit mon_fri_planning' claim is repeated twice, the full output-field list is unnecessary alongside an output schema, and one sentence is garbled. It is serviceable but not tight.

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 three-parameter deterministic calculator with an output schema and rich annotations, the description covers the determinism guarantee, holiday policy, scope exclusions, formula, and REST fallback, so an agent has everything needed to call it. The redundant output enumeration is the only surplus.

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 start_date, working_days and work_schedule, and the description largely restates them (including the sample JSON and the 'excluded for non-zero offsets' semantics already in the schema). Baseline 3 is appropriate when the structured schema carries the parameter burden.

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 opens with a specific verb+resource+scope: it 'adds or subtracts Slovenia authority-scope working days in exact coverage.' An agent can distinguish it from check_si_working_day (single-day test) and count_si_working_days (counting within a range) 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?

'Use this when you need a deterministic Slovenia working-day offset' plus the explicit exclusion list (individual shifts, replacement weekly rest, employer/sector/school/bank schedules, payroll, legal deadlines, future years) gives clear context for use and non-use. It falls short of 5 because the 'Do not use this when slovenia 2026 statutory work-free dates over an explicitly selected Monday-Friday planning baseline' clause is grammatically incoherent, and no sibling alternative is named.

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