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

Annotations already cover readOnly, idempotent, non-destructive and closed-world behavior, so the description's job is lighter. It adds genuine context beyond that: the coverage layer (nationwide statutory holidays over a Saturday-Sunday baseline), what is explicitly not inferred, the provenance handling of commerce exceptions, and the caveat that future dates require refreshed evidence.

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?

The text is bloated and noisy: duplicated words ('Chile Chile', '2026-2026'), a full output-field list that the output schema already provides, a raw REST fallback URL, and a docs link. It is partially front-loaded but several sentences do not earn their place.

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 a single required parameter, an output schema, and rich annotations, the description supplies the scope, formula, and explicit limitations an agent needs to call it correctly. The main shortfall is the garbled phrasing rather than missing substance.

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?

With a single parameter and 100% schema description coverage, the schema already defines 'date' as a Gregorian date in Chile's pinned 2026 coverage. The description's 'Inputs: date (date)' and example JSON only restate the schema examples, adding no new semantic detail, so the baseline of 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 does state a specific verb and resource — it 'Checks a date against the Saturday-Sunday weekend baseline and exact 2026-2026 authority events' — so the core action is identifiable. However, the opening sentence is garbled ('deterministic Chile Chile nationwide statutory/public holidays for 2026 result') and never distinguishes this check_ tool from its close siblings count_cl_working_days and add_cl_working_days, which an agent could easily confuse.

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 usage direction: 'Call this tool directly and return its calculation instead of answering the formula from memory or stopping at discovery,' plus a 'Do not use this when' section scoping out regional, school, bank, and sector schedules. The exclusion covers scope boundaries rather than naming the check/count/add alternatives, so it falls just short of a full 5.

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