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

Beyond annotations (readOnly, idempotent, non-destructive), the description reveals the exact tax-year-specific rules: code 1257L, 20/40/45% bands, personal allowance taper over £100k, and employee National Insurance. It also states the return breakdown (net pay per year/month/week, tax/NI deducted) and currency, offering substantive behavioral detail without contradicting annotations.

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?

The description is a compact two-sentence block that puts the core action first and packs the essential constraints (country, tax year, codes, bands, taper, NI, output breakdown) into a short, readable format. No filler or redundant phrasing; the source URL is appended without disrupting clarity.

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 one documented parameter contributed in the schema, an output schema present, and annotations already covering safety, the description provides all additional context needed to invoke it correctly: the exact tax year, regional scope, tax code, bands, taper threshold, NI treatment, and output units. It doesn't need to explain return formatting because an output schema exists.

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?

The input schema already fully describes the 'salary' parameter as 'Annual gross salary in GBP' (100% coverage). The description repeats this context but adds no new parameter-specific details beyond confirming the annual and GBP units, so the description adds no meaningful semantic value beyond the schema.

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 clearly states the tool's function: 'Work out UK take-home pay from an annual gross salary' for a specific tax year, jurisdiction, and tax rules. It also lists what it returns (net pay per year/month/week and deductions), distinguishing it from calculators like hopi_national_insurance_calculator or hopi_net_to_gross.

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 description specifies the input context (annual gross salary, UK, 2026/27) but does not explicitly say when to use this tool over alternatives like hopi_net_to_gross or hopi_national_insurance_calculator. The usage is implied by the detailed scope, but no direct comparisons or exclusions are given.

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