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

Annotations only declare readOnlyHint and openWorldHint; the description goes further by disclosing the cost model (x402 USDC on Base, pay-per-call) and the failure-path behavior that the response returns a payment challenge when payment is missing. That is meaningful context an agent cannot infer from structured fields.

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, front-loaded with the resource and scope before the payment caveat. Every clause carries information; the parenthetical '(official)' is the only slightly soft element.

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 an output schema present, return values need no explanation, and the description covers the critical non-obvious behavior (payment challenge). For a zero-required-param lookup tool this is nearly complete, though it says nothing about unsupported countries or failure modes beyond payment.

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% with both parameters documented (year format/default, country ISO code), so the schema carries the burden. The description adds nothing parameter-specific beyond the country/year scope already implied.

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?

Names a specific resource (public holidays) with scope qualifiers (any country/year, official). It is unambiguous and clearly distinct from every sibling, which are all finance/crypto/market tools, but it lacks an explicit verb framing (list/retrieve).

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?

No statement of when to use this versus alternatives, nor prerequisites such as needing a funded wallet. The only contextual cue is the payment model, which is behavioral rather than usage guidance.

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