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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, so the safety profile is covered; the description's 'Read-only' largely repeats it. It still adds real behavioral context the annotations cannot: the ranking is restricted to one catalogue, results carry explicit match reasons and considerations, a published 'from' price and product URL, and prices/availability may change so the product page is authoritative.

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?

Front-loaded with the trigger condition, and every sentence carries routing, exclusion, or return-value information; little is filler. It is a dense single paragraph rather than a structured block, and the 'Read-only' clause duplicates the annotations, but the length is justified by the breadth of the exclusion list.

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 9-parameter, output-schema-backed recommendation tool with rich annotations, the description covers everything the agent needs: trigger, alternative, hard exclusions, what the results contain, and the staleness caveat on prices. Return-value detail is correctly left to the output schema, and no prerequisite information is missing.

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 all nine parameters including enums, limits and the ryokan-only semantics (meal_plan, group_size, private_onsen). The description only gestures at the same fields ('area, interests, budget, private onsen or meal plan') without adding format or behavioural detail beyond the schema, so the 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 specific verb and resource ('recommend... bookable Japan tours, activities, cultural experiences, tickets, ryokan') and immediately narrows scope: 'ranks only OlaChill catalogue items against the supplied criteria.' It also names the sibling it is not (search_travel_products), so an agent can distinguish the two without opening either schema.

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?

Explicit trigger phrasing ('recommendations, suggestions, a shortlist, what should we do'), an explicit alternative with its selecting condition ('Use search_travel_products instead when the user names a specific product... exact inventory lookup'), and an explicit exclusion list (helicopter flights, transfers, hotels other than ryokan, restaurants, weather, visas). Nothing is left to inference.

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