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

Annotations already declare readOnly, idempotent, non-destructive, and closed-world, so the safety profile is covered. The description adds genuinely new behavioral facts: the counting base is Korea time (KST) with today as default, weeks start on Monday, and the result includes a Korean business-day determination — none of which annotations convey. It stops short of describing output field names or error behavior for unparseable expressions.

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 core purpose and output shape lead, followed by the expression inventory and conventions. The long quoted enumeration is dense but functional since it defines accepted input syntax; the closing 'use this instead of working out weekdays' line is a well-placed routing hint rather than filler.

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?

No output schema exists, yet the description names what comes back: an exact date, a weekday, and whether it is a Korean business day. Combined with the KST default, Monday week start, and the 100-expression cap in the schema, an agent has everything needed to call this correctly.

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 baseline is 3, but the description earns more by giving the actual grammar of the 'expressions' array — relative days, business days, named weekdays, week-relative phrases, month/월일 forms, year-end — which the schema only labels as 'Korean expressions'. It also reinforces that base_date is interpreted in KST, not the caller's timezone.

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 and resource: converts Korean relative date expressions into exact dates and weekdays, anchored on a KST base date, and additionally reports Korean business-day status. The concrete expression inventory makes the scope unmistakable, and the output shape (date, weekday, business day) is stated 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?

Explicitly advises 'Use this instead of working out weekdays yourself,' which sets the intent against agent-side arithmetic. It does not name sibling alternatives such as kr_add_business_days or kr_business_day, so an agent handling '3영업일 후' versus a pure holiday lookup has to infer the boundary itself.

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