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

readOnlyHint=true already tells the agent this is safe and non-mutating, and the description adds genuinely new behavior: a $0.05 per-call charge and, importantly, that out-of-window years are rejected without being billed. That billing-failure nuance is not derivable from annotations or schema. What is missing is any statement about latency, rate limits, or response shape beyond the field list.

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 sentences, no filler; the resource and returned fields are front-loaded, followed by the failure/billing caveat. The leading price tag occupies prime space but is defensible for a metered tool. Slightly dense mid-sentence phrasing but nothing that fails to earn its place.

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 carries the return-value burden and does so by naming the three returned attributes. Two optional parameters and a single read-only lookup keep complexity low, so the definition is nearly sufficient. A brief note on date format or ordering would close the 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 description coverage is 100%, so both the 'year' range/default and the 'upcoming' filter are already documented; that sets the baseline at 3. The description echoes the 2021-2027 window and clarifies that each row carries a days-away figure, which indirectly explains what 'upcoming' filters on, but it adds no syntax or format detail beyond the schema.

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 (Indonesian national public holidays and joint-leave days for a given year) and enumerates exactly what comes back: dates, Indonesian and English names, and days-away. It does not, however, distinguish itself from close siblings such as indonesia_holiday_check, indonesia_workdays, or indonesia_next_working_day, so an agent must infer the split.

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?

Usage is only implied: fetch the holiday list for a year. There is no explicit 'use this instead of X' routing toward indonesia_holiday_check or indonesia_workdays, which are the obvious alternatives. Positively, the description does state a hard boundary — years outside 2021-2027 are refused with a machine-readable reason — which is a real usage constraint.

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