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

Annotations already declare readOnly/idempotent/non-destructive/closed-world, so the bar is lower; the description still adds real context by disclosing the calendar authority scope, the substitute-day and holiday policy outputs, and a dataset version. It does not contradict the annotations.

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?

Front-loaded with use-when guidance and organized into labeled sections (do not use, what it computes, inputs, outputs, formula, fallback, docs), so it is easy to scan. Some content (example requests, output field list, formula) is boilerplate padding given an output schema already exists.

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 deterministic read-only count tool with a full output schema, the definition covers scope limits, inputs, and a REST fallback endpoint and docs link. An agent has everything needed to invoke it correctly and interpret the result.

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% and all four parameters are documented in the schema, including defaults, so the description's 'Inputs:' line largely restates the schema. The bundled JSON example adds slight value for correct invocation, but there is little semantic meaning beyond what the schema already carries.

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 a specific verb+resource ('Counts authority-scope working and non-working dates in a range') for Portugal, which separates it from single-date checks and add-day tools by implication. It does not name a sibling explicitly, so the differentiation rests on the range/count framing rather than direct routing language.

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?

Gives an explicit when-to-use ('when you need an auditable Portugal working-day count' and 'call this tool directly ... instead of answering from memory') and an explicit scope exclusion (municipal, autonomous-region, collective-agreement, employer and locally substituted schedules are not inferred). It stops short of naming the alternative sibling tool (e.g. check_pt_working_day) for the excluded cases.

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