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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint and openWorldHint, so safety is covered. The description's one added behavioral note—'same engine, cache and limits as GET /v1/is-business-day'—hints at caching and rate limiting but is vague and never quantifies them. 'Read-only' merely repeats the annotation.

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?

Purpose is front-loaded in the first sentence with no wasted preamble, and the whole description is three tight sentences. Minor slack comes from 'Read-only' (redundant with annotations) and an HTTP endpoint reference of limited value to an agent choosing a tool.

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 an output schema present, the description needn't explain full return values, and annotations carry the safety profile; the description stays within its lane and covers scope adequately. It is nearly complete, only slightly under-specified on the caching/limits it alludes to.

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 all five parameters are self-documented with formats, patterns and defaults. The description only broadly gestures at country/region and weekends/holidays, adding no syntax or constraint detail beyond the schema, so baseline 3 applies.

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 predicate verb and resource: checking whether a given date is a business day, scoped by country and region. This is distinguishable from the arithmetic siblings (add_business_days, business_days_between), but the description never names those alternatives to reinforce the distinction.

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?

The description explains the domain (weekends and public holidays) but gives no when-to-use guidance and never contrasts itself with siblings like business_days_between or get_holidays. An agent must infer that this is the single-date predicate tool from the name alone.

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