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

With no annotations, the description carries the full burden and does disclose meaningful behavior: weekends are excluded, public holidays are NOT excluded so the result is an upper bound, and the call costs $0.005. This is solid disclosure, though it omits endpoint inclusivity (are 'from' and 'to' counted?) and behavior when from > to.

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?

Three short sentences, front-loaded with the core behavior, then the intended use, then the important caveat and cost. Every sentence earns its place with no filler.

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 two-parameter tool with no output schema or annotations, the description covers the main behavioral risks (weekends, holiday exclusion, cost). It is nearly complete, missing only endpoint inclusivity and edge-case behavior such as reversed dates.

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% and both parameters carry format descriptions ('YYYY-MM-DD'), so the schema already does the heavy lifting. The description adds no parameter-level meaning beyond the schema and leaves the important inclusivity question unresolved.

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 ('Count') and resource ('business days between two dates') with an explicit scope qualifier ('excluding weekends'). This distinguishes it clearly from siblings like weekday_of, time_until, and convert_duration, which deal with different temporal questions.

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 it to turn a calendar deadline into a working-day deadline' gives a concrete use context, which is better than most. It does not, however, name alternatives or state when another sibling (e.g. convert_duration) would be preferred, so it stops short of explicit routing guidance.

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