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

No annotations are provided, so the description carries the burden, and it discloses the output content beyond the name: it returns closure info plus the next/previous business day. That is meaningful behavioral context for a read-only query with no output schema, though it says nothing about invalid dates or calendar defaults.

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 front-loaded sentence that packs the check, the calendar scoping, and the return content with no filler. The semicolon-clause is dense but 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?

With no output schema, the description usefully summarises what comes back (closures, adjacent business day), which is the key missing piece an agent would otherwise lack. It stops short of noting error behavior for invalid dates, but the tool's low complexity makes that a minor gap.

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 schema already documents the YYYY-MM-DD date format and the extensive calendar id examples. The description adds no parameter detail beyond noting 'on a calendar', 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?

States a specific verb (check) and resource (whether a date is a business day on a calendar), and clarifies scope with the calendar parameter. It is distinguishable from add_business_days/count_business_days/list_holidays by its yes/no-per-date nature, but it never names a sibling to sharpen the contrast.

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?

Usage is implied by the purpose: call it when you need a per-date business-day verdict for a given calendar. There is no explicit when-to-use versus add_business_days (which shifts a date) or today_status (which is today-only), and no stated prerequisites or exclusions.

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