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

Annotations already cover read-only/idempotent/non-destructive, and the description adds real context: the response includes every dated period with legal basis, source, and confidence, and no computation is performed. This is behavior beyond the annotation set, though pagination or volume expectations are not mentioned.

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?

One dense but well-structured sentence with the scope and the reference-data caveat front-loaded, followed by the returned content. Zero filler, though the parenthetical acronym chain is slightly heavy.

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 compensates by enumerating what comes back (bands, threshold, reliefs, dated periods, legal basis, source, confidence). Combined with annotations, an agent has enough to call it correctly; only response shape/pagination detail is absent.

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 coverage is 100%, so both parameters are already documented, including the YYYY-MM-DD format, the today default, and ISO alpha-2 country examples. The description only restates the date-scoping semantics at a high level, adding little 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?

States a specific verb+resource: income tax bands on employment income for resident employees, including bands, tax-free threshold, reliefs, and dated periods with legal basis. It also explicitly distances itself from calculation siblings with 'Reference data only, no salary 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?

Clearly signals the when-not case (do not use this to compute salary tax; use a calculation tool instead) and frames the tool as a lookup of in-force reference data. It stops short of naming the alternative sibling like calculate_withholding_tax or get_withholding_tax explicitly.

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