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

Annotations already declare readOnly, idempotent, non-destructive, and closed-world behavior, so the safety profile is covered. The description still adds value beyond them with the 'UK only' geographic constraint, the 'Free' cost signal (analogous to rate/cost disclosure), and the enumeration of returned content. It omits data freshness/update cadence for deadlines, which is the one remaining behavioral gap.

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?

Three short sentences, front-loaded with the hard constraint ('UK only') and the returned content, closing with a single-word cost note. No filler and nothing buried.

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-optional-parameter, closed-world, read-only lookup with no output schema, the description enumerates the returned fields and both invocation modes, which is enough to call it correctly. It stops short of noting how current the deadline data is or how areas map to the enum values.

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 single enum parameter is fully documented in the schema, so the baseline is 3. The description's 'one area, or a list of every area' merely restates the optionality already expressed in the schema ('Optional. Leave out to list every area.') without adding format or selection guidance.

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?

Specific verb ('Returns') plus a concrete resource list: tourist tax rules, start dates, next return deadlines, and Wales registration duty. It also states scope ('UK only') and coverage (one area or all areas). It does not, however, name or differentiate itself from the sibling calculate_uk_tourist_tax, so the boundary between 'rules lookup' and 'tax calculation' is left implicit.

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?

'for one area, or a list of every area' implicitly tells the agent how to use the optional parameter, and 'Free' signals there is no cost barrier to calling it. But there is no explicit when-to-use guidance and no mention of when to prefer the sibling calculate_uk_tourist_tax instead, so usage is inferred rather than stated.

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