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

Annotations already cover readOnly/idempotent/non-destructive, and the description adds genuinely new behavioral facts: deterministic calculation, the exact formula, pinned 2026 coverage, unencoded proposed holidays, and an explicit instruction to return the result rather than reason from memory. That is substantial value beyond the structured fields.

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?

Sections are front-loaded logically, but the prose is bloated with duplicated tokens ('Vietnam Vietnam', '2026-2026'), repeated example sets, and a garbled negated clause ('Do not use this when public-sector and statutory paid-holiday layer only'). Useful signal exists but is padded.

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 fields need not be enumerated, yet the description still lists them harmlessly. Coverage scope, limitations, formula, and a REST fallback are all present; only the 2026-only coverage bound and the malformed exclusion clause keep it from being fully airtight.

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% and the single date parameter is fully documented in the schema, including its 2026-coverage caveat. The description's 'Inputs: date (date)' and JSON examples largely restate what the schema already provides, so the baseline 3 applies.

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: 'Checks a date against the Saturday-Sunday weekend baseline and exact 2026-2026 authority events' for Vietnam's public sector. It is clearly a single-date checker rather than a bulk add/count tool, though it never names a sibling directly, so differentiation comes mostly from the scope sentence.

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 an explicit 'Use this when...' directive and a 'Do not use this when...' exclusion that enumerates what is not inferred (private-employer, non-Sat/Sun workweeks, provincial, sector, bank, school schedules) plus a not-yet-approved holiday caveat. This is about as complete a usage contract as a one-parameter tool can carry.

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