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

Beyond the readOnly/idempotent annotations, the description discloses that weekends and public holidays are skipped, that skipped holidays are listed in the result, that local weekend conventions vary (Fri-Sat in SA/EG), and critically that calls cost $0.002 USDC via x402 on Base mainnet. The payment/metering detail is high-value context the annotations do not cover. It stops short of describing edge behavior (invalid country, out-of-range days).

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?

Front-loaded with the core action and scope, then behavior, then use cases, then cost. Dense but each clause carries information; the pricing sentence is slightly awkward at the tail but is not 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 three-parameter tool with full schema coverage and no output schema, the description covers what the tool does, what it returns (the skipped holidays), localization caveats, and the payment requirement. Only the error/failure modes are unaddressed.

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 adds meaning beyond the schema: 'adds or subtracts' explains that a negative 'days' value subtracts, and it reinforces country scope (220+ vs. the 11 verified calendars listed in the schema). The date-format and range details are left to the schema, which already handles them.

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?

Specific verb pair ('adds or subtracts working days') and resource ('business days from a date'), with scope quantified as 220+ countries and weekend/holiday-skipping behavior. It clearly differs from siblings like za_count_business_days and za_is_business_day by what it does to a date, though it never names those siblings explicitly.

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?

Concrete use cases are supplied ('net 5 business days', notice periods, SLAs, delivery estimates, legal deadlines), which gives an agent a clear signal for when to reach for this tool. However, no when-not-to-use guidance or explicit routing to the sibling counting/checking tools is provided.

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