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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so the safety profile is covered. The description adds the valuable behavioural facts the annotations lack: jurisdiction (UK), the effective date floor, and that it returns the applicable rate alongside the check.

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 sentence that states the check, the inputs that drive it, and the effective date with no filler. The phrasing 'for the worker's age, and apprenticeship, on a date from 1 April 2024' is slightly awkward but not costly.

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?

With five all-required parameters fully documented in schema, complete annotations, and an output schema covering the return value, the description only needs to supply the non-structural context — which it does (UK scope, 1 April 2024 start, returns applicable rate). What happens for out-of-range dates or unsupported worker categories remains unstated.

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 coverage is 100%, so every parameter including the subtle pastSchoolAge flag is already documented, establishing a baseline of 3. The description adds only the date-floor constraint on 'date'; it says nothing about the pastSchoolAge or apprentice enum values that materially change the result.

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 names a specific verb and resource ('Check whether an hourly rate of pay meets the UK minimum wage') and even states the criteria used (age, apprenticeship, date). It does not explicitly distinguish itself from any sibling, but the domain is unambiguous against check_holiday_entitlement or check_deposit_cap.

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?

It supplies clear applicability context: the check is UK-specific and only valid for a date from 1 April 2024, which is a real precondition an agent must respect. It gives no explicit exclusions (e.g. agricultural wages or salaried staff), so it stops short of full when/when-not guidance.

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