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

Annotations already declare this a read-only, idempotent read, so the bar is lower. The description still adds real semantics: regional plans enumerate covered countries and absence from that list means no coverage, plus an explicit note that prices/plans are current at call time. That is genuinely beyond the annotations.

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 tight sentences, front-loaded with the core payload and immediately followed by the regional-coverage caveat. The closing freshness sentence is slightly redundant but does useful work signaling non-cached results.

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?

An output schema exists, so return structure need not be spelled out; the description nonetheless flags the two facts an agent would otherwise miss (country list semantics, live pricing). Complete enough to call correctly, with only the missing sibling routing as a gap.

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 the schema already documents currency, unlimited and destination. The description only loosely reinforces 'one destination' and 'live prices' and adds no parameter syntax or format detail, so baseline 3 applies.

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 concrete resource (plans on sale for one destination) plus the payload contents (live prices, data, validity, product URL). It is specific enough to distinguish from search_destinations/fetch, but never names or contrasts a sibling, so it stops short of a 5.

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?

Usage is only implied: you need a destination, and the schema points at search_destinations for the slug. The description itself gives no when-to-use or when-not guidance and no routing away from siblings.

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