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

Beyond the readOnlyHint/openWorldHint annotations, it discloses the return shape (business-day boolean, weekend-vs-holiday reason, next business day), the presence of a `today` block, and the `date_anchor_warning` behavior with a concrete failure example. This is precisely the kind of non-obvious behavioral detail annotations cannot carry.

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?

Front-loaded with the core purpose, then progressively adds behavior and examples. The date-anchor digression and its parenthetical '(2025-07-20 is a Sunday, 2026-08-20 is a Thursday)' are justified by the failure mode they prevent, though the mid-sentence line wrapping makes it slightly denser than needed.

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 annotations covering the safety profile and an output schema covering the return structure, the description supplies exactly the missing pieces: the reason codes, the next-business-day field, and the date-resolution/warning semantics. An agent has everything needed to call and interpret it correctly.

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 both parameters are already documented as ISO 8601 date and ISO 3166-1 alpha-2 code. The description only reinforces this indirectly through examples; it adds no new format, constraint, or edge-case meaning beyond the schema. 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 first sentence gives a precise verb+resource+scope ('Check if a specific date is a business day in a country'), and the following sentences clarify what factors into the answer (country-specific weekends, public holidays). It is unmistakable what the tool does, but it never distinguishes itself from the closely related sibling 'bank_holidays' or 'value_date', leaving the agent to infer the boundary.

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?

It gives actionable invocation guidance rather than tool-selection guidance: resolve relative dates against the server's `today` block, and heed `date_anchor_warning` for past check_dates. That is real when-to-use-this-way context, but there is no statement of when to prefer this over 'bank_holidays' or other date/holiday siblings.

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