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

Annotations cover the safety profile (readOnlyHint, destructiveHint=false, openWorldHint), so the bar is lower. The description adds real value beyond them: it discloses the return shape (live fares when available, always Google Flights and Skyscanner links) and the booking boundary, which matters since there is no output schema.

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 sentences, front-loaded with scope and examples, then return behavior, then the booking boundary. Efficient and each sentence carries information, though the inline example list is slightly heavy for what it contributes.

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 an 8-param search tool with no output schema, the description adequately explains what comes back (fares + external links) and sets expectations when live fares are absent. Combined with annotations covering safety, the main omission is any mention of round-trip vs one-way handling tied to return_date.

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 sits at 50%: from/to/date have descriptions but cabin, adults, infants, and children do not. The description's airport examples largely duplicate the schema's from/to examples and add no meaning for the undocumented parameters, so it neither compensates for the gap nor falls to a 1-2.

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+resource (search flights) with an explicit geographic scope (to and within Thailand). The resource itself cleanly separates it from search_hotels, search_transfers, and search_experiences, so an agent can pick it without opening the 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?

Usage is implied by the resource, and the closing note 'The traveller books flights with the airline' signals that this tool does not complete bookings, which is a useful boundary. However, it gives no explicit when-to-use vs ask_travel_guides/plan_trip guidance and does not name alternatives.

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