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

Annotations already declare readOnly/idempotent/openWorld=false, so the safety profile is covered; the description adds genuine behavioral context such as 2026-only coverage, what is explicitly not inferred, the deterministic weekend+authority-event formula, and a REST fallback URL. This goes beyond restating annotations.

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?

There is a duplicated 'South Korea South Korea' phrase and an awkward '2026-2026' range, plus a long, run-on 'Do not use this when...' clause. The useful content is buried rather than front-loaded.

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?

With an output schema present, the description need not explain return values, yet it still lists the fields, adds coverage/scope limits and a fallback endpoint. For a single-parameter read-only checker, the description is essentially complete despite the wording flaws.

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% and only one parameter exists, so the schema already carries the parameter meaning; the description merely restates 'Inputs: date (date)' and provides JSON examples that duplicate the schema's examples. Baseline 3 is appropriate.

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 does state a specific verb+resource (check a date against South Korea statutory/public-office holidays for 2026), but the opening sentence is garbled with duplicated text ('deterministic South Korea South Korea statutory public holidays...result'), which muddies the intent. It names the territory but does not distinguish itself from the sibling check/count/add_kr_working_day tools beyond the country label.

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 says when to use it ('Call this tool directly and return its calculation instead of answering the formula from memory') and gives a when-not boundary covering private-employer, school, bank, exchange, local-government, and 2027 schedules not being inferred. It does not, however, tell the agent to prefer this over the sibling count_kr/add_kr tools.

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