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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, so no further action is expected. The description adds behavioral context beyond the schema by specifying the US scope and the internal rule (weekday and not a federal holiday), which clarifies exactly what is being evaluated. No contradiction with annotations.

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 clear sentence with no filler. The verb and resource are front-loaded, and the parenthetical definition efficiently explains the logic. Every word earns its place.

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 one-parameter, read-only predicate tool, this description is essentially complete. The return value is implied as boolean by 'Check whether.' The US qualifier handles geographic scope, and the holiday definition is explicit. The only minor gap is not stating the response format outright, but it is not necessary for such a simple 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?

The schema fully documents the single parameter as an ISO date (100% schema coverage), so the baseline applies. The description does not add parameter-format details, but it does add meaning to the date by framing it as a 'US date' in the context of the business-day check. This adds modest value but is not essential.

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 states a specific verb ('Check whether'), a clear resource ('a US date'), and the exact predicate ('business day (weekday and not a federal holiday)'). This fully distinguishes it from sibling tools like calendar_business_days_add or calendar_holidays without requiring schema inspection.

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 description makes the tool's use case obvious: call when you need to know if a given date is a US business day. However, it does not explicitly mention when not to use it or point to alternatives (e.g., calendar_business_days_add for adding business days, calendar_holidays for holiday lists). Usage is implied, not contrasted.

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