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

With no annotations the description carries the full burden, and it does disclose one genuinely useful behavioral detail: the counting boundary is exclusive of from_date and inclusive of to_date, which pre-empts off-by-one errors. It omits everything else an agent needs — rule resolution, how region/jurisdiction alter the result, the NZ default, and error behavior.

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?

A single tight sentence with the counting window front-loaded and zero filler. The phrasing 'after from_date up to and including to_date' is slightly awkward but is the most information-dense part of the definition.

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?

An output schema exists, so return values need no explanation, but for a five-parameter tool with no annotations and 0% schema coverage the definition is thin. An agent cannot tell which rule values are legal or how region/jurisdiction affect the count without trial and error.

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 0% across five parameters, so the description must compensate and mostly does not. It names from_date, to_date and rule but adds no format, expected values, or meaning for region and jurisdiction, and gives no hint about valid rule identifiers.

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 resource ('Count working days') plus the counting window, which cleanly separates it from the sibling add_working_days. However, it never explains what a 'rule' is or how this differs from the other date/holiday siblings like list_rules or nz_holidays.

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?

No when-to-use or when-not-to-use guidance, and no mention of alternatives despite four plausible sibling tools. The phrase 'under a rule' implies a required rule input but never says how to obtain a valid rule (e.g., via list_rules) or what happens if the rule is unknown.

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