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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, so the safety profile is fully covered. The description adds genuinely useful domain context in the HU swap-Saturday quirk and the 30+ country coverage, which explains why results may differ from naive calendar math. It does not disclose what is returned (a count? a date? per-country breakdown) or how locale edge cases are resolved.

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?

One sentence plus a parenthetical endpoint reference: front-loaded, no filler, no repetition of the title. The endpoint detail is arguably the least useful piece for an agent, but it costs only a parenthetical.

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 no output schema, the description carries the burden of explaining the response, and it does not — an agent cannot tell whether it receives a day count, a deadline date, or a holiday list. Parameter coverage is handled by the schema and the holiday-rule nuance is present, so it is adequate but leaves a real gap for a calculator-style tool.

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%, so the three parameters are already documented with examples, making the baseline a 3. The description adds some meaning for `country` by noting 30+ countries and the HU-specific rule, but says nothing extra about start_date/end_date semantics (inclusive vs. exclusive, format, tie to the required/optional split).

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 gives a specific verb and resource ('Calculate business days and SLA deadlines') plus a concrete scope ('across 30+ countries including HU swap Saturdays'). It is unambiguous and, since no sibling tool covers calendar/holiday math, an agent can identify it without further checking. It stops short of a 5 only because it never contrasts itself with any alternative.

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?

There is no explicit when-to-use or when-not-to-use guidance; the only operational hint is the literal endpoint string. The description does not say whether end_date is optional, what happens if it is omitted, or what use case (SLA calculation vs. business-day counting) each mode serves. The agent must infer all invocation context.

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