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

Annotations already declare read-only, idempotent, and closed-world behavior, but the description adds substantial value: it specifies the return content (reason, next/previous business days), documents local weekend handling (Friday–Saturday in Saudi Arabia, Egypt, Israel), observed holidays, verified calendars for named countries, and even the per-call price.

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 core function is front-loaded, and every clause adds useful information. However, the description is one long sentence with many clauses, so readability could be improved by splitting it into two or three sentences.

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?

With no output schema, the description fully explains what the tool returns and covers important edge cases like non-standard weekends and observed holidays. Nothing essential for an agent to call it correctly is missing.

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 the schema already documents date format and country code examples. The description adds no parameter-specific syntax or constraints beyond what the schema provides, making the baseline 3 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 ('Checks whether a date is a business day'), the resource (a single date), and scope (220+ countries). It also clarifies the result includes the reason and adjacent business days, which distinguishes it from sibling tools like za_count_business_days or za_add_business_days.

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?

Gives use cases (payment, settlement, delivery dates) but does not explicitly say when to choose this over za_count_business_days or za_add_business_days, nor does it state when not to use it. Usage is implied rather than directed.

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