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

With no annotations, the description carries the full burden and does well: it discloses the upstream data source, that substitute/temporary holidays are included only once promulgated (a real freshness caveat), the exact response shape, and notably the monetization model — $0.0027 USDC via x402 on Base or Solana. It does not mention rate limits, error behavior for out-of-range years, or caching, which keeps it from a 5.

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?

Dense but front-loaded: the "Use when" clause leads, followed by labeled fragments for data source, input, output, example, and price. Every segment carries information, though the telegraphic labeling style ("Data:", "Input:", "Price:") reads more like a spec sheet than prose.

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?

There is no output schema, and the description compensates by enumerating the returned fields (date, weekday, Korean and English name, isPublicHoliday, kind). Combined with the input range, source, and payment requirement, an agent has everything needed to call it 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% and the single parameter's description already states the YYYY format and the 2004–2100 bounds. The description repeats that range and adds only a usage example (?year=2026), so it adds little meaning beyond the schema — baseline 3.

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 (South Korea's official public holidays for a year) and pins down the data source (KASI special-day register) plus the scope that matters for correctness (substitute and temporary holidays once promulgated). No sibling covers holidays, so it is unambiguously the right tool for this need.

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 when you need ... (business-day calculation, scheduling, settlement and payroll calendars)" gives concrete triggering contexts, which is more than most definitions offer. It stops short of naming exclusions or pointing to any alternative (e.g. a generic calendar/time tool such as time_convert), so it is clear but not fully routed.

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