calculate_uk_income_tax

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

The description adds behavioral traits beyond annotations: 'Read-only, deterministic, estimate only' and details about the personal allowance taper above £100k. This goes beyond the readOnlyHint and other annotations, providing useful context about the tool's behavior and limitations.

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 concise (4 sentences) and front-loaded: it starts with the core purpose, then gives usage guidelines, input, outputs, and properties. Every sentence adds value; no fluff.

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?

Given the simple schema (one parameter, no output schema), the description is complete. It details input, output fields, tax year, bands, taper, and exclusions. It also explains return values since there is no output schema.

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 schema already describes 'income' as 'Annual gross income in GBP' with a minimum of 0. The description reiterates this but adds no new semantic information. With 100% schema coverage, baseline 3 is appropriate.

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 what the tool does: calculates UK income tax for 2025/26 using HMRC bands, including personal allowance taper. It distinguishes itself from siblings by specifying geographic scope (England/Wales/NI) and exclusions (Scottish bands, National Insurance).

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 explicitly states when to use: for England/Wales/NI income tax questions. It also specifies what is not included (National Insurance, Scottish bands). It could be improved by naming alternative tools for Scottish or NI tax, but the context is clear enough.

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