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

Annotations already cover safety (readOnlyHint, destructiveHint=false, openWorldHint), but the description adds real context: computed from statutory rules, validity window 2024-2100, weekend observance shifting the observed weekday, and the billing model ($0.01/call, first 25 free, failed calls free, repeats not free) which explains the non-idempotent hint. 'Reads or computes only and changes nothing' largely restates the annotations, which keeps it from a 5.

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 resource and coverage come first, followed by output fields, then constraints and pricing, so the important content is front-loaded. The pricing/compute sentence is slightly run-on and mixes payment, side-effect and caching semantics in one clause, costing some readability.

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-shape burden and does so by naming date, local name, English name and observed weekday. It also discloses the computation source and year window; only edge behavior (unsupported country, empty result) is unaddressed.

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 coverage is 100%, so the baseline is 3, but the description adds meaning beyond the schema by spelling out that GB/UK resolves to England and Wales only and by listing the supported country set alongside the schema's code format. The year range is duplicated from the schema and the 'default this year' behavior is left to 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?

States a specific verb and resource (list nationwide public holidays for a year) and enumerates both the covered countries and the returned fields (date, local and English name, observed weekday). It does not name the nearby siblings (date_business_days, date_info, cron_next) it should be distinguished from, so an agent must infer the boundary itself.

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?

'Use for scheduling, delivery dates and business-day maths' gives an implied context, and the country=SE example shows the expected input shape. There is no when-not guidance and no explicit mention of the overlapping date_business_days tool, so the agent gets no stated alternative or exclusion.

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