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

Annotations already declare readOnlyHint=true, idempotentHint=true, openWorldHint=false and destructiveHint=false, so the safety profile is fully covered. The description adds the supported-country scope, which is useful, but says nothing about error behavior for unsupported countries or how the two result shapes differ.

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?

Two tight sentences with the primary operation front-loaded and the country enumeration last, so nothing important is buried. The first sentence is dense but every clause carries information.

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 5-parameter, no-output-schema tool, the description covers the modes and the country domain but leaves output shape, error conditions, and the interaction rules between date/from/to/add_business_days unstated. It is adequate but not fully self-contained.

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 coverage is 80%; the only undocumented parameter is add_business_days, and the description supplies its meaning ('the date N business days later/earlier') plus the date it is relative to. It also reinforces the from/to versus date pairing. It stops short of stating required combinations (e.g. that add_business_days needs date), which is the remaining gap.

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 two concrete operations on a specific resource: listing public holidays for a country between two dates, and checking whether a date is a business day / offsetting by N business days. The generic name 'calendar' is rescued by the description, and no sibling tool overlaps this domain, so sibling differentiation isn't needed.

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 only implied through parameter pairing ('between two dates' for the holiday list, 'a date' for the business-day check). There is no explicit statement of when to pick each mode, nor what happens if the modes are mixed or a country outside the listed set is supplied.

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