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

Annotations already declare readOnly, openWorld, idempotent, and non-destructive, so the safety bar is lower. The description adds genuinely useful behavior beyond that: it returns airport codes, booking comparison links to Aviasales/Kiwi/Skyscanner/Google Flights, and recently seen cheapest fares, and it warns that quoted prices fluctuate and the authoritative live price is on the booking site.

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 tight sentences, front-loaded with what the tool does, followed by what it returns and the key caveat about live pricing. No wasted wording.

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?

With no output schema, the description must explain return values, and it does: airport codes, booking links, and cheapest-seen fares. Combined with 83% schema coverage and rich annotations, this is nearly complete, only missing explicit one-way/round-trip and passenger-count framing.

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 83%, so the schema itself documents origin, destination, dates, currency, and adults well. The description adds little parameter-level meaning beyond "for given dates" and does not elaborate on currency, passenger count, or one-way behavior — baseline 3 is appropriate when the schema does the heavy lifting.

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: "Find flights between two cities or airports for given dates." The resource (flights) is clearly distinct from siblings like search_hotels and search_transfers, though it does not explicitly name a sibling it displaces.

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 rather than spelled out — an agent can infer this is the tool for flight lookups, and the note that prices change and live fares live on the booking site gives useful context about the results' nature. However, there is no explicit when-to-use/when-not guidance, no mention of one-way vs round-trip handling beyond what the schema implies, and no routing to alternatives.

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