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

Annotations already declare readOnly/idempotent/non-destructive, so the bar is lower, and the description still adds real behavioral substance: the supported range 2022-01-01 to 2035-12-31, the legal basis of the holiday set (Law 2429 + Diyanet), and the half-day rule applied from 13:00. It stops short of stating what happens for out-of-range or reversed dates, which is the one remaining behavioral gap.

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 short sentences, each carrying distinct information (scope, range, business-day definition, half-day rule) with the most important scope and inclusive-boundary facts front-loaded. No filler or restatement of the title.

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 an output schema present, return values need not be explained, and the description covers the interpretive ambiguities that matter: inclusive endpoints, holiday model, supported date range, and half-day treatment. Only edge-case behavior (dates outside 2022–2035, to < from) is left unstated.

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 extra by specifying that both endpoints are included, a semantic the schema does not state. It also characterizes the calendar variants at a business level (administrative leave from 2026, no central-bank bulletin on eves), reinforcing rather than merely repeating the enum documentation.

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?

A precise verb+resource ('Counts business days') with explicit jurisdiction (Türkiye) and inclusive-boundary semantics, which is much more specific than the sibling 'check_business_day'. It never names the siblings, so an agent must infer the distinction from the verb alone, but the counting-between-dates framing is distinctive enough to separate it.

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?

Usage is implied by the tool's framing rather than stated: the agent can infer this is for counting days across a range versus checking a single date or adding days. There is no explicit when-to-use/when-not statement and no reference to add_business_days, check_business_day or list_holidays as alternatives.

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