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

Annotations already declare readOnly/idempotent/non-destructive, so the bar is lower, and the description still adds two genuinely useful facts: the legal-data cut-off ('rules as of 2026-08-15') and the shape of the returned records (datum, name, bundesweit). No output schema exists, so naming the key fields is real added value; pagination or ordering behavior is not mentioned.

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 capability sentence and the scope constraint are front-loaded, and the sibling cross-reference is placed where it prevents a misroute. The four German example utterances are helpful disambiguators but partially duplicate the prose above them, costing some density.

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 only two parameters, no output schema and annotations covering the safety profile, the description supplies what's missing: data currency, the returned field names, and a sibling boundary. Only the absence of ordering/pagination detail and any note about years outside the supported range keeps it from 5.

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 the year range and the enum of 16 state codes are already documented in the schema. The description only restates the nationwide-vs-state distinction that the 'land' property description already makes, adding no format or semantics beyond it.

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 ('Lists the public holidays of a year in Germany') plus the scope variants (nationwide vs. one of 16 federal states). It explicitly routes working-day arithmetic to the sibling count_working_days, so an agent can separate it from the nearest alternative without opening either schema.

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?

Names the triggering request shape ('which public holidays fall in a year or month in a given state') and hands the working-day use case to count_working_days. It never states what the tool cannot do (e.g., non-German holidays, dates outside 2020–2040 are only implied by the schema), so it lacks explicit exclusions.

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