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

Annotations declare readOnlyHint=false and idempotentHint=false, and the description explains why: each successful call costs $0.001 in USDC on Base via x402, so it is not a free/idempotent read. The 'per successful call' phrasing also clarifies billing on failure. It does not detail error/retry behavior, keeping it below a 5.

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 purpose, then coverage, use cases, and cost. Every sentence contributes, though the country enumeration and payment sentence make it slightly long. Still efficient and well-ordered.

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?

There is no output schema, but the description specifies the return fields (date, local and English name, observed weekday) and the billing model, covering the essentials. Failure/error semantics are the only notable omission.

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 100%, so baseline is 3. The description adds meaning beyond the ISO-code schema: it maps GB to 'England and Wales' and US to 'federal', and confirms the 2024-2100 year range. This usefully disambiguates the country parameter's scope.

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 a specific resource (nationwide public holidays), enumerates the covered countries, lists the returned fields (date, local and English name, observed weekday), and states the coverage window (2024-2100). An agent can immediately tell this apart from every sibling.

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 concrete use cases ('scheduling, delivery dates and business-day maths'), which sets the context clearly. It does not name alternatives or exclusions, but no sibling overlaps functionally, so the gap is minor.

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