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

With annotations already covering readOnly/idempotent/non-destructive/non-openWorld, the description goes further: it discloses the computation approach ("move one day at a time; decrement only on status.is_working_day=true"), the explicit coverage boundary (nationwide mandatory list only, no municipal/employer schedules), and a direct REST fallback endpoint. That is meaningful behavior 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?

The labeled-section format is front-loaded and easy to scan, but several blocks duplicate structured data the agent already has: "Inputs" restates the schema, "Complete JSON argument examples" duplicates the schema example, and "Outputs" duplicates the output schema. The "Example user requests" lines ("around Ordinary weekday") are filler.

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 2-parameter tool with full schema coverage, rich annotations, and an output schema, the description covers usage, scope limits, computation, and fallback more than adequately. The only excess is enumerating output fields, which the output schema already owns.

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 both parameters (date range, signed offset semantics, bounds). The description restates the inputs and repeats an example identical to the schema's, adding no syntax or constraint detail the schema lacks. Baseline 3 is correct.

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 (adds/subtracts) and resource (Portugal authority-scope working days), and adds differentiating scope language ("authority-scope", "exact coverage") that separates it from the global/regional siblings. It does not explicitly distinguish itself from its closest siblings add_global_working_days or count_pt_working_days, so the differentiation is only partial.

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?

"Use this when you need a deterministic Portugal working-day offset. Call this tool directly and return its calculation instead of answering the formula from memory" gives a clear when-to-use and even an anti-pattern (don't answer from memory). The negative clause about municipal/autonomous-region/collective-agreement holidays defines when the tool's coverage does NOT apply, though the sentence is grammatically garbled and no alternative tool is named.

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