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

Annotations declare a read-only, idempotent, non-destructive, closed-world operation, so safety is well covered. The description adds that the comparison is sourced from Payotte's guides and their official sources, which gives useful provenance context. It says nothing about freshness, pagination, or output shape, but with this annotation profile the bar is lower.

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 dense sentence that front-loads the scope (UNITED KINGDOM, one rule across four nations) and then enumerates topics. It is compact and waste-free, though the long parenthetical is slightly heavy for a description that chiefly restates the enum.

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?

For a one-parameter, annotated, read-only comparison tool, the description covers scope, source, and topic coverage adequately. The absence of an output schema leaves the return shape undocumented, but that is minor given the tool's straightforward nature.

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% and the enum fully enumerates the eight allowed topics, so the schema carries the parameter contract. The description's parenthetical list of topics mirrors the enum exactly, adding no new semantics beyond confirmation. Baseline 4 is appropriate when the schema is this complete.

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 (compared) and resource (one rule across the four UK nations), and names the eight topics it can compare. The sibling 'compare_states_*' tools cover other countries, and 'purchase_tax_uk' is a single-topic cousin – an agent can distinguish this cross-nation comparison tool immediately.

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 implies when to use it (when you need a rule compared across all four UK nations) but gives no explicit when-not-to-use or alternative routing. With 'purchase_tax_uk' present as a sibling, a sentence on when to prefer this cross-nation view over the single-rule tool would have helped.

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