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

Annotations already cover readOnly/idempotent/non-destructive/openWorld, so the description is free to add non-obvious behavior, and it does: uncovered schedule layers, preserved-as-provenance mandatory-rest exceptions, evidence-freshness requirements for future dates, substitute-day/holiday policy outputs, and a pinned REST fallback path with an explicit '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?

Use conditions are front-loaded, but the body bloats: an output-field list that duplicates the output schema, a trivial formula line ('working_days += status.is_working_day'), and a REST URL plus docs link. Working content is diluted by restatement.

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 date-range counting tool with a full output schema and strong annotations, the description covers scope limits, examples, an argument JSON example, and a fallback endpoint. Listing return fields is redundant given the output schema, but nothing critical to correct invocation 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 all four parameters. The description only restates the inputs with their types and marks include_start_date/include_end_date as optional, adding no format, boundary, or interaction meaning beyond what the schema provides. 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 ('Counts authority-scope working and non-working dates in a range') for Chile, which separates it from the many per-country count_*_working_days siblings. It also names the covered scope (nationwide statutory/public-holiday layer over a Saturday-Sunday baseline). The downstream 'Do not use this when...' sentence is garbled, but the computing purpose itself is unambiguous.

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 use conditions ('when you need an auditable Chile working-day count', 'call this tool directly... instead of answering the formula from memory') and explicit exclusions (regional/local holidays, school, bank, private-employer and collective-agreement schedules are not inferred; future dates need refreshed evidence). The malformed 'Do not use this when...' clause blunts the routing statement but the exclusion content is present.

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