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

Annotations already declare readOnlyHint, idempotentHint and destructiveHint=false, so safety is covered; the description adds the end-date/inclusive boundary rule, the returned components (business, weekend, holiday counts plus holiday list), and a note about shared engine, cache and limits. The only weakness is that 'limits' is left undefined.

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?

Four short sentences, front-loaded with the core purpose before the boundary rule and the return/limit notes. The trailing reference to 'GET /v1/between' is slightly off-target for an agent but costs little.

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?

For a 7-parameter tool with an output schema, the description covers purpose, boundary semantics, and return content, so an agent can call it correctly. Minor gaps remain around what 'limits' means and error behavior, but return-value details are rightly left to the output schema.

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 country, region, types, weekend, from/to and inclusive are all documented in the schema. The description only reinforces the inclusive flag's effect on counting, adding little beyond the schema text — baseline 3 is appropriate.

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 ('Count business days between two dates') with explicit scope ('in a country (and region), excluding weekends and public holidays'). This clearly separates it from siblings like is_business_day (single-day check), add_business_days (date arithmetic), and get_holidays (holiday listing).

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 implies when the tool applies ('between two dates') and clarifies the end-date exclusion rule, but it never names an alternative or states when NOT to use it. An agent choosing between this and get_holidays or add_business_days gets no routing guidance.

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