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

Annotations already declare readOnly, idempotent and non-destructive, so safety is covered. The description adds real behavioral value beyond them by specifying the return content: net profit and effective tax rate for each structure plus which structure pays less this year. It does not mention assumptions such as tax-year or rate versions.

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?

Two sentences, zero waste, front-loaded with the comparison subject before the return-value summary. Every clause carries information.

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 no output schema, the description correctly compensates by naming the returned metrics and the verdict field. Annotations cover safety, and the schema covers inputs, so the definition is near-complete; only modeling assumptions (tax year, rate basis) are 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 description coverage is 100%, so all five parameters are already documented with units and semantics (including the 'omit to extract all post-tax profit' nuance). The description adds no parameter-level detail beyond the schema, which matches the baseline 3.

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 ('Compares') and a precise resource: annual tax on a UK rental property held personally (Section 24) vs inside a limited company (corporation tax + dividend tax). This clearly distinguishes it from siblings like calculate_section_24_tax or calculate_capital_gains_tax, which cover only one side of the comparison.

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 comparison scope implies when the tool applies (choosing between personal and company ownership), but there is no explicit when-to-use statement, no prerequisites, and no routing to alternatives such as calculate_section_24_tax for personal-only analysis.

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