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

With no annotations, the description carries the full burden, and it does disclose one genuinely useful behavior: the operation costs 1 credit. However, it does not state what is returned, and it is silent on the notable fact that all three inputs are optional (what happens if only daysPerWeek or only hoursPerWeek is passed, or none at all).

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?

A single front-loaded clause plus a parenthetical cost note, with no filler. The trade-off is that the brevity leaves the usage and return-value gaps unfilled, but nothing written is wasted.

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 calculation tool with no output schema and no annotations, the description should say what the result looks like (entitlement in days or hours) and how the optional inputs combine. Neither is covered, so an agent cannot predict the response shape or the default behavior when parameters are omitted.

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 nominally 100%, but the schema text is near-contentless ('number', 'number 0-12'), so the baseline of 3 applies rather than a penalty. The description's phrase 'working pattern, pro rata by months' is the only thing signalling that daysPerWeek/hoursPerWeek are alternative ways to express the pattern and monthsWorked drives proration.

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?

Names a specific resource (statutory paid holiday entitlement) and its calculation basis (working pattern, pro rata by months), which separates it from sibling calendar tools like bank_holidays, public_holidays and working_days. The verb is only implied ('for a working pattern'), but the resource and scope are unambiguous.

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?

No when-to-use or when-not-to-use guidance is given, and no alternative is named despite several adjacent holiday/days siblings. An agent must infer that this computes entitlement rather than listing holidays, and gets no hint about which of the optional inputs to supply.

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