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

Annotations already declare readOnlyHint, idempotentHint and destructiveHint=false, so safety is covered; the description adds real behavioral context: weekend days, public holidays and make-up working days are factored in per country, and start is excluded from counts. It does not discuss return format or edge cases like range limits, but the added semantics are solid.

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?

Three dense sentences, front-loaded with the primary operation, with each clause (inclusive end, negative N, start not counted, Japan flag) carrying distinct information. Nothing is redundant.

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?

For a 7-parameter date tool with no output schema, the description covers both modes, country-specific holiday logic, and the one non-obvious flag. It leaves the exact return shape (count vs. date string) only implicit and does not explain region or include_government beyond the schema text.

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 parameters are already documented, and the description adds some meaning beyond it: the sign convention for add, the exclusion of start, and the concrete Japan year-end window (12/29-1/3) that the schema only labels 'Japan only'. Baseline 3 applies since the schema carries most of the load.

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 two specific verbs (count business days between start/end, or find the date N business days from start) on a named resource. This is clearly the counting/offset tool, distinguishable from siblings like list_holidays or find_long_weekends, though it never explicitly names those alternatives.

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?

Explains how to select each mode: end for counting, add=N for forward offset, negative N for backward, and start itself is not counted. It also gives a conditional instruction (For Japan, set year_end_closed), but does not state when to prefer this tool over the sibling date tools.

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