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

Beyond the annotations (readOnly/idempotent/non-destructive), the description discloses the algorithm ('move one day at a time; decrement only on status.is_working_day=true'), the exact coverage limitation (public-sector/statutory layer only), an unencoded edge case (2026 Vietnam Cultural Day arrangement), and a REST fallback path with a 'do not guess another /api/* path' warning.

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?

It is well front-loaded with usage and exclusions, but includes redundant sections: an Outputs list duplicating the existing output schema, a JSON argument example duplicating the schema's examples, and example user requests. These repeat structured data rather than adding value, blunting conciseness.

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?

Given the tool is a scoped date calculator with full schema coverage, rich annotations, and an existing output schema, the description covers everything an agent needs: scope, exclusions, formula, edge cases, and a REST fallback. Nothing material 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 start_date and working_days including the signed-offset and start-date-exclusion semantics. The description adds only a short Inputs recap and a redundant JSON example, so the baseline of 3 is 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?

The description states a specific verb and resource ('adds or subtracts Vietnam authority-scope working days') and scopes it to Vietnam, distinguishing it from the many country-specific siblings like add_th_working_days or add_singapore_working_days without opening any schema.

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?

It gives explicit when-to-use ('when you need a deterministic Vietnam working-day offset... return its calculation instead of answering from memory') and an explicit when-not-to-use block (private-employer, non-Sat/Sun workweeks, provincial, sector, bank, school and employer schedules are not inferred). This is exactly the routing guidance an agent needs.

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