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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive), so the bar is lower; the description still adds real context by disclosing the rules year, last-updated stamp, and that results include engine outputs, sources with lastChecked dates and a disclaimer. It stops short of describing pagination or row limits, but for a pure calculator this is solid.

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 the calculation formula and unit, followed by versioning and return-shape notes; no sentence is pure filler. The trailing 'Inputs marked "Only used when"...' line is meta-commentary that doesn't map to anything in the schema and could be dropped.

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 three-parameter calculator with no output schema, the description does necessary work: it explains the return payload composition and the rules vintage the agent is relying on. Combined with 100% schema coverage, an agent has enough to invoke it correctly; only cross-tool routing guidance 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 explains weeklyHours, monthsWorked and leaveTakenHours thoroughly; the description adds only the pro-rating intent, which the schema also states. The sentence about inputs 'marked "Only used when"' refers to markers that do not appear in the provided schema, which is mildly confusing rather than additive.

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 resource ('Statutory vacation leave in Malta for 2026'), a concrete unit (hours), and even the composition of the figure (192-hour base plus 24 weekend-holiday hours, pro-rated). This clearly separates it from sibling country/benefit calculators without needing 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?

Usage is implied by the country-and-benefit scoping of the name, but the description never states when to reach for this versus another calculator (e.g. greece_annual_leave, latvia_vacation_pay) or any precondition such as 'for 2026 employment only'. Nothing misleads, but the agent must infer routing.

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