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

Annotations already declare readOnly, idempotent and closed-world behavior, so the bar is lower. The description still earns credit for disclosing that lunar and government-proclaimed dates are rule-based estimates — an accuracy caveat an agent cannot get from annotations — plus the $0.001 x402 payment cost, which affects invocation decisions.

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?

Three short sentences, front-loaded with what the tool returns and bounded by coverage, followed by the accuracy caveat and cost. Nothing is redundant and nothing buries the important facts.

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 two-parameter lookup with an output schema, the description covers scope, data-quality caveats and cost — most of what an agent needs. It omits behavior outside the supported range (e.g. a year past 2050 or an unsupported country), which is the only remaining 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 coverage is 100%, so both parameters are already documented, including the year default and the ISO alpha-2 pattern. The description's '207 countries, 2000–2050' restates ranges already present in the schema, adding no format or edge-case detail.

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 the resource and its two dimensions precisely ('Public holidays for a country and year') and bounds the dataset (207 countries, 2000–2050). It does not explicitly contrast itself with the nearest sibling, business_hours_deadline, though the country parameter text hints at that link.

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?

Use is implied by the stated scope — an agent can infer this is the lookup for holiday calendars — but there is no explicit when-to-use or when-not-to-use guidance, and no pointer to business_hours_deadline as the alternative when business-day math is the actual goal.

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