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

Annotations already declare readOnlyHint and openWorldHint, yet the description adds substantive context beyond them: bridge days are defined (one or two days of leave joining a holiday to a weekend), offers may be returned, and sponsored: true offers are paid placements that must be labelled as sponsored. That last point is a genuine disclosure an agent could not 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?

Roughly three sentences, front-loaded with what is returned before the usage trigger. The middle sentence is dense but each clause (holidays, offers, sponsored flag) carries distinct information, so little is wasted.

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?

An output schema exists, so return shape need not be documented, yet the description still tells the agent what categories of results arrive and how to treat sponsored offers. Combined with annotations covering the safety profile, nothing an agent needs to select or call this tool correctly is missing.

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 country and year are already documented in the schema, including the 2-letter-or-English-name format and the current-year default. The description only restates the country/year framing ('in a country for a year') without adding format or edge-case detail, so the baseline of 3 applies.

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 verb and resource ('Lists every long weekend in a country for a year') and enumerates the payload: leave-free long weekends, bridge days, nationwide public holidays and travel offers. The scope wording ('every ... for a year') implicitly separates it from the singular sibling next_long_weekend, but no sibling is named explicitly, so it falls short of full differentiation.

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 states clearly when to reach for it: 'Use it when someone asks about public holidays, long weekends, bridge days or the best days to take off.' That is a genuine trigger list. It does not say when NOT to use it or point to alternatives such as next_long_weekend for a single quick answer or plan_annual_leave for leave planning.

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