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

Annotations cover the safety profile (readOnly, idempotent, non-destructive), and the description goes well beyond them: it discloses the exact 2026 holiday package and Monday-Friday baseline, the stepwise decrement formula, the deterministic nature, and a concrete REST fallback path with a warning not to guess other /api/* paths.

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?

Labelled sections (use/do-not-use/what it computes/inputs/outputs/formula/fallback/docs) are front-loaded and scannable, but the output-field list duplicates the existing output schema and the formula/REST details add bulk for a two-parameter tool.

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?

Everything needed to select and invoke the tool is present: routing rules, a worked example request, complete JSON arguments, and the calculation semantics. The enumeration of output fields is redundant given the output schema exists, but completeness is not in question.

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 already 100%, and the two parameters are self-evident (start_date, working_days). The description restates the inputs and provides a full JSON example, but adds no syntax or edge-case meaning beyond what the schema documents (e.g. non-zero-offset exclusivity is already in the schema).

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 with scope: deterministic UAE federal-government working-day offset for 2026. It explicitly distinguishes itself from the sibling check_/count_ tools and from non-federal calendars by naming what it does not cover.

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 clause, an explicit do-not-use clause (private employer, local government, future years), and instructs the agent to call the tool rather than answer from memory. This is textbook routing guidance.

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