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

Annotations already declare readOnlyHint and openWorldHint, so safety is covered. The description adds genuinely useful behavior beyond that: the weekend-plus-official-holiday exclusion rule, the returned holiday list, and the payment/authentication model ($0.005 USDC per call via x402 on Base), which an agent must know before invoking.

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?

Two dense sentences, front-loaded with the operation and its boundary rule; the pricing detail is tucked at the end where it belongs. No 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?

For a two-param read-only tool with no output schema, the description covers scope, holiday handling, result contents ('with the holidays in range'), and cost. The only meaningful omission is the expected date input format.

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 0%, so the description must compensate. It does add the critical inclusivity semantics for 'from' and 'to', but gives no date format (e.g., ISO 8601), leaving a real ambiguity that an agent will hit on the first call.

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 ('Count Korean business days between two dates') and pins down the exact boundary semantics: exclusive of 'from', inclusive of 'to'. An agent can distinguish this from siblings kr_business_day_add and kr_business_day_check purely from the description.

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?

The boundary rule and holiday exclusion imply when this tool applies, but the description never routes the agent explicitly to or away from the close siblings (kr_business_day_check for single dates, kr_business_day_add for shifting). Usage is inferable but not guided.

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