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

Annotations already declare readOnly, idempotent, openWorld and non-destructive, so the safety profile is covered. The description adds value beyond that by disclosing coverage breadth (225 countries and territories) and the shape of the payload ('what each rate applies to'), but says nothing about how the date defaults, data freshness, or handling of countries with no VAT.

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 packs the resource, coverage count, optional temporal dimension, and return content with no filler.

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?

A read-only lookup with full schema coverage and complete annotations needs little more, and the description does sketch the return content in the absence of an output schema. Minor gap: no note on default date behavior or freshness, which matters for a rates tool.

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%: the country param already documents ISO code or English name and the date param already documents YYYY-MM-DD semantics. The description restates the country/date duality without adding format or edge-case detail, so baseline 3 applies.

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 (standard and reduced VAT/GST rates) with explicit scope: per country, optionally on a date, plus rate applicability. Nothing in the sibling list (insolvency, ownership, sanctions, company search) overlaps, so confusion risk is nil, though the description never explicitly positions itself against alternatives.

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?

'Optionally on a given date' implies historical rate lookups, which is the only usage cue. There is no statement of when to use this versus another tool, no prerequisites, and no exclusions (e.g. whether non-VAT territories are covered).

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