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

Goes well past the readOnly/idempotent annotations: it discloses the holiday basis (Law 2429 plus Diyanet), the supported date window, the Mon-Fri-minus-holidays rule, and that the start date is excluded. The half-day-from-13:00 rule is the kind of edge case an agent would otherwise get wrong.

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?

Four tight sentences, front-loaded with the return semantics before the calendar and half-day caveats. No redundant restatement of the tool name or schema types.

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?

Output schema covers the return value and annotations cover safety, so what remains is domain rules, which the description supplies thoroughly including the validity window. The one gap is that the `calendar` parameter options, a meaningful mode switch, are never explained in prose.

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; the description adds real meaning by explaining negative `days` and the half-day concept behind the `half_days` enum. It does not, however, describe the three `calendar` modes (standard/public_sector/tcmb), which are left entirely to the schema.

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 and result ('Returns the date that is N business days after ... a start date in Türkiye'), which unambiguously separates it from count_business_days and check_business_day. The scope (Türkiye, 2022-2035, official calendar) is concrete and verifiable.

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 motivating use cases (payment terms, legal deadlines) and the negative-N convention for going backwards, which tells an agent when this is the right tool. It never names the siblings or explicitly rules out counting/checking use cases, so the differentiation stays implicit.

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