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

Annotations cover the safety profile (readOnly, idempotent, openWorld), but the description goes further by disclosing the data source, the holiday attribute set (date, names, nationwide vs county-limited, fixed vs movable, types), that the data is public and non-personal, and the paid x402 USDC model with per-call price and the PaymentRequired-on-unpaid-call behavior. That payment semantics is information annotations cannot carry. It stops short of noting rate limits or any caching/retry behavior.

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 use case and the core outcome before details, and every clause carries information (source, attributes, payment). The 'Public, non-personal data' clause is slightly expendable, but nothing is padded verbosely.

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 no output schema, the description usefully enumerates the returned per-holiday fields and coverage, so an agent knows what it gets back. The main gap is sibling disambiguation among the holiday tools, which is not addressed.

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 (country as ISO 3166-1 alpha-2, year defaulting to current UTC year). The description only adds illustrative country codes (LT, US, DE, JP), which is a marginal gain over the schema. Baseline 3 is appropriate.

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?

States a precise verb and resource ('returns every public holiday for a country in a given year') plus the data source (Nager.Date) and country coverage (~100 countries). The scope is unambiguous, but it never distinguishes itself from the four sibling holiday tools (holiday_check, holidays_next, holidays_countries, holidays_long_weekend), which an agent will see side by side.

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?

Gives concrete usage contexts — scheduling, payroll calendars, travel planning, 'is the office closed?' — which is a clear statement of when to reach for it. However, it offers no exclusions or alternative routing despite four closely related holiday siblings, so the agent must infer which one to pick.

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