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

Annotations already declare readOnlyHint=true, destructiveHint=false, openWorldHint=true and idempotentHint=false, so the safety profile is covered by structured data. The description still adds real value beyond that: the per-call price and payment mechanisms, the fact that failed calls are free, that repeats are charged (reinforcing non-idempotence in practical terms), and that it 'changes nothing.' Only return formatting/pagination is left unstated.

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?

The content is front-loaded: what it returns comes first, then use cases, then the example, then cost and side-effect notes. Every sentence carries information. It is dense rather than padded, though the pricing/payment clause is long-winded relative to the rest and would read better split or condensed.

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?

There is no output schema, but the description compensates by enumerating the returned fields, so an agent knows what to expect. It also covers cost, side effects, and country/year inputs. A minor gap: it never states what happens when year is omitted, though the schema does supply that default.

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% — the schema already documents country as an ISO 3166-1 alpha-2 code or English name and year as 2024-2100 with a default of the current year. The description adds only a single illustration ('Example: country=SE') and no format or edge-case detail beyond the schema. Baseline 3 applies when the structured schema does the heavy lifting.

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 first sentence names a specific resource (public holidays) with a concrete verb-implied operation, scope (country + year, 100+ countries), and enumerates the returned fields (date, local/English name, nationwide flag, observed day). An agent knows exactly what this returns. It does not differentiate itself from the sibling 'holidays' tool, which is the only thing keeping it from a 5.

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?

Explicit use cases are given: 'plan deliveries, schedules and business days, or to tell whether today is a holiday somewhere.' That is clear positive guidance for when to reach for this tool. It stops short of a 5 because no exclusion or explicit alternative is named for the case where the agent might want a different holidays-related sibling.

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