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

Annotations already declare readOnly/idempotent/non-destructive/closed-world, and the description goes well beyond them by disclosing the exact algorithm ('move one day at a time; decrement only on status.is_working_day=true'), the calendar scope limitation, a deterministic REST fallback endpoint, and the docs URL. Nothing about behavior is left implicit.

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-loads the routing guidance well, but then enumerates all 17 output fields even though an output schema exists, and adds formula/fallback/docs sections. The Outputs list in particular is redundant bloat that duplicates structured data.

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 2-parameter tool with full schema coverage, an output schema, and rich annotations, the description supplies the remaining pieces an agent needs: the authoritative scope boundary, the deterministic-computation mandate, fallback endpoint, and documentation link.

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 both parameters (start_date, working_days) are already fully documented in the schema including the signed-offset semantics. The description's 'Inputs:' line and JSON example merely restate what the schema already provides, adding no new parameter meaning.

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+scope: 'Adds or subtracts Brazil authority-scope working days in exact coverage.' An agent can distinguish this from the dozens of sibling add_*_working_days tools for other jurisdictions without opening the schema.

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?

Explicit when-to-use ('call this tool directly and return its calculation instead of answering from memory or stopping at discovery') and when-not ('Do not use this when this is not a universal Brazilian private-employer calendar; state, municipal, sector, employer and private payroll schedules are not inferred'). This is a genuinely calibrated routing statement.

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