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

Annotations already cover read-only/idempotent/non-destructive, and the description adds real behavioral context beyond them: determinism, the explicit mon_fri_planning baseline requirement, that education-only holidays (e.g. November 1) create no general rest, and that future years and local/sector closures are unsupported. The 'Do not use this when...' sentence is syntactically broken, which slightly undersells these constraints.

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 text is repetitive and malformed: 'Bulgaria Bulgaria', a broken 'Do not use this when' clause, and a 20-field outputs enumeration that duplicates the existing output schema. The REST fallback and docs links are useful, but a large share of the content 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?

An output schema exists, so the long output list is redundant; the description would be complete with just the coverage limits, baseline requirement, and fallback endpoint. The core constraints are present but buried under duplicate and garbled prose.

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% for both parameters, so the schema already defines date and the work_schedule enum. The description reinforces that mon_fri_planning is explicitly required and supplies argument examples, but adds little semantic detail beyond the schema.

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 'What it computes' line states a specific verb and resource: checks a date against a Saturday-Sunday weekend baseline plus exact 2026 Bulgaria authority events. The country scope and single-date semantics distinguish it from the count_*/add_* siblings, though the opening sentence is garbled ('Bulgaria Bulgaria 2026 nationwide rest-day facts') and obscures the purpose.

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 gives both a when ('Use this when you need deterministic ... planning baseline result') and a when-not (personal, shift, school, employer, bank, optional religious-leave, payroll, legal-deadline schedules are not computed; future years unsupported). It also tells the agent to call it rather than answer from memory. It never names the sibling count_bg_working_days or add_bg_working_days as the alternative for multi-day range work.

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