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

Annotations already mark the operation as read-only, idempotent, and non-destructive. The description adds meaningful behavioral context beyond that: it aggregates inventory from Viator, GetYourGuide, Klook, and Groupon and returns booking links, plus a platform filter via source. No contradiction with 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?

Two sentences with no filler. The core action and data scope come first, followed by a precise usage trigger and a source-filter hint, so an agent can parse it quickly.

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 search tool with full schema descriptions and clear enums, the description is complete: it states what is searched, what is returned, and when to use it. No output schema exists, but the description's 'returns tours from... with booking links' gives enough situational context for invocation.

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 documentation covers 100% of parameters with clear descriptions and enums, so the schema carries the semantic load. The description reinforces keyword/island/price/platform concepts but does not add substantive meaning beyond the schema, making the baseline 3 appropriate.

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?

The description opens with a specific verb and resource: 'Search 1,500+ bookable Hawaii tours and activities', which immediately identifies the tool's scope. It also lists the aggregators and differentiates from sibling tools by focusing on tours/activities rather than restaurants, events, deals, or weather.

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?

It gives an explicit use condition: 'Use this when users ask about Hawaii tours, activities, or things to do.' It does not name sibling alternatives or state when not to use it, so it stops short of a full when/when-not comparison.

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