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

Annotations already declare read-only, idempotent, non-destructive, and closed-world behavior. The description adds useful behavioral context beyond annotations: the external data sources and the three-year maximum range, though it does not cover error behavior or response shape.

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 description is front-loaded with the core purpose, followed by a concrete example and a key constraint. Every sentence earns its place with no redundant or vague wording.

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?

Given the rich schema descriptions, full annotations, and an output schema, the description provides everything needed to select and invoke the tool correctly. It covers purpose, sources, region types, date modes, and range limits without duplicating structured fields.

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. The description adds meaning by clarifying the two query modes (year vs. between two dates), the up-to-three-year range limit, and how region maps to UK regions versus ISO country codes.

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 states a specific verb and resource: list bank holidays or public holidays for a region in a year or date range. It also names the underlying sources (gov.uk vs. Nager.Date) and outputs (weekdays and substitute days), which clearly distinguishes it from sibling tools like get_school_holidays.

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 gives a clear usage context with an example question, so an agent knows this is for bank/public holiday queries. However, it does not explicitly say when not to use it or name alternatives such as get_school_holidays or plan_leave_year.

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