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

No annotations are provided, so the description carries the full burden. It discloses the cost ($0.02), payment methods (api_key or x402), range limit (366 days), receipt behavior (included on paid success, not on unpaid 402), legal disclaimer, verification method, and handling of unknown subdivision (free refusal with list). This is comprehensive and leaves no critical behavioral surprises.

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?

The description is long but packed with necessary details. It front-loads the core purpose and cost, then proceeds to range, payment, receipt, verification, and subdivision. Every sentence earns its place, though it could be tightened by moving the legal disclaimer to a secondary note. It remains well-structured and scannable.

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?

Given there is no output schema, the description explicitly states what is returned (holidays hit by name and the next working day after the range). It covers payment flow, edge cases (unknown subdivision, unpaid refusal), and verification. The tool has multiple parameters and a paid model, and the description addresses all relevant aspects an agent needs to call it correctly.

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%, but the description adds substantial meaning beyond the schema. It explains that api_key is optional and how payment works without it, clarifies receipt behavior and its relationship to verification, and details subdivision usage including the fallback to get_public_holidays for region lists and the free refusal for unknown codes. These enrich the schema definitions meaningfully.

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?

The description states a specific verb and resource: 'Working days in a date range for a country,' and details what it does (weekends, statutory holidays, Egypt's Fri–Sat handling). It also distinguishes itself from related SKUs by clarifying it is not a series certified extract and referencing verify_answer_receipt and get_public_holidays for complementary functionality. This makes the tool's purpose unmistakable.

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 provides clear context for when to use the tool (counting working days) and references related tools for specific needs (get_public_holidays for region listings, verify_answer_receipt for verification). However, it does not explicitly state exclusions or conditions for choosing this tool over alternatives, such as 'use get_public_holidays when you only need the list of holidays.' The payment and receipt guidance is useful but not about tool selection.

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