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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world), so the bar is lower, and the description still adds real value: it discloses that every field of each tour is returned, that no winner/score/verdict is produced, and that nulls remain null. That last point is an important expectation-setter an agent could otherwise misread.

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, front-loaded sentences with no filler, and the negative disclosure ('no winner, score or verdict') is placed prominently. Minor redundancy between 'with the same fields' and 'returns every field of each tour' keeps it just under a 5.

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 read-only comparison tool with an output schema present and annotations covering safety, the description is nearly sufficient: return shape, scope, and the absence of a verdict are all addressed. Missing only usage/routing guidance and any note on invalid or duplicate slugs.

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 67%: currency and language carry their own descriptions and the slugs array documents minItems/maxItems/uniqueItems, so the schema does most of the work. The description's 'two to four tours' reinforces the slugs cardinality and adds the 'same fields' comparison semantics, but no new format or syntax detail.

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 ('compare') and resource ('tours'), and pins the scope at two to four tours, which the agent can immediately distinguish from single-tour tools like get_tour. It falls short of a 5 only because it never names a sibling to route against.

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 explains mechanics and output shape but gives no when-to-use context or alternative: no guidance on choosing this over get_tour for one tour or search_tours when merely browsing candidates. Nothing is misleading, but the agent gets no routing help.

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