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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the safety profile is covered. The description adds genuinely useful behavior — weekends and public holidays are skipped — but does not say that holidays depend on the country parameter, nor what happens if the result itself falls on a holiday. That omission matters for an openWorldHint tool whose output varies by region.

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?

A single front-loaded sentence with the key behavior clause in the same breath. Nothing is wasted and nothing is buried.

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?

There is no output schema, so the description should indicate the return value — presumably a date, but the format and whether it matches the YYYY-MM-DD input are unstated. For a simple three-parameter tool this is close to adequate, but the return shape and country-holiday dependency leave real gaps.

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, but the description earns more by clarifying the unit of 'days' as business days rather than calendar days — an ambiguity the schema's bare 'Non-negative integer' leaves open. The country parameter's effect on which holidays are skipped is still not explained in prose.

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 ('add') and resource ('business days to a start date') plus the defining behavior ('skipping weekends and public holidays'), which is enough to distinguish it from sibling is_business_day. It stops short of naming any sibling explicitly, so an agent must infer the boundary itself.

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?

No when-to-use, when-not-to-use, or alternative routing is given. Nothing tells the agent to prefer is_business_day for single-date checks or resolve_expression for holiday-aware expression parsing, so tool selection relies entirely on name matching.

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