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

With no annotations, the description carries the disclosure burden and does reasonably well: it explains the calculation method (90% for 6 weeks, then lower of flat rate or 90%), pins the rate to a specific tax year (£194.32 for 2026-27) and warns it changes each April. The 'estimate only, not advice' caveat is a valuable editorial trait. It stops short of saying what happens if both earnings inputs are omitted, which matters given zero required parameters.

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 core purpose before the rate detail, and every clause carries information. The rate figure and the April-change warning are slightly heavy for a one-liner but are genuinely useful, so waste is minimal.

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?

No annotations and no output schema, so the description must explain the computation and the disclaimer, and it does. The remaining gap is the optional-parameter story — nothing tells the agent what the tool does when neither annualSalary nor weeklyEarnings is provided.

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 are already documented, and the baseline is 3. The description's phrase 'average weekly earnings' loosely mirrors weeklyEarnings but adds no syntax, units beyond GBP, or guidance on how annualSalary vs weeklyEarnings interact when both are supplied.

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 and resource — 'Estimate UK Statutory Maternity Pay' — with the scope nailed down to the 39 weeks and gov.uk rules. It is immediately distinguishable from the siblings (due date, ovulation, pregnancy weeks), none of which touch pay calculation.

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?

The domain is clear enough that an agent can infer when to reach for it, and 'Estimate only, not advice' sets a boundary on how to present results. However, there is no explicit statement of when NOT to use it or what alternative exists for related pay questions, so guidance is implied rather than stated.

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