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 still adds real value by defining what counts as a business day (weekends plus national public holidays), which is behavioral semantics not present in any structured field. It stops short of covering invalid country codes or regional/sub-national holiday handling.

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?

A single compact sentence with the key definition front-loaded in the parenthetical, and zero wasted words. The clipped grammar ('Whether a date is...') makes it read as a fragment rather than a complete statement, which slightly reduces clarity.

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?

This is a simple two-parameter predicate with full schema documentation, rich annotations, and no output schema, so the description need not explain return values. The only meaningful gap is the absence of any note on invalid or unsupported country codes, which is a minor omission for a tool of this complexity.

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%: both parameters carry patterns and concrete examples (ISO 3166-1 alpha-2 country codes, YYYY-MM-DD dates). The description adds nothing about either parameter, so the baseline 3 applies.

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 names the resource (a date, in a country) and the check performed (whether it is a working day), which is specific enough to distinguish it from siblings like count_business_days and add_business_days. It is a noun fragment rather than a verb phrase, and it does not explicitly contrast itself with those siblings, so it falls just short of a 5.

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 when-to-use guidance, no stated preconditions, and no mention of the closely related siblings (count_business_days, add_business_days, get_public_holidays) that an agent could confuse this with. Usage is only inferable from the tool name itself.

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