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

Annotations already mark this read-only and open-world; the description adds genuinely non-obvious context — fares are recent cached prices that may change at booking. That freshness caveat is exactly the extra layer annotations can't convey. It stops short of stating coverage/refresh cadence.

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, front-loaded with the core purpose, then the freshness caveat and result linkage. Efficient, with no filler.

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 usefully tells the agent that each result links to the vidi.one flights page, and the cache caveat sets expectations about price stability. Minor gap: nothing about result limits or how 'cheapest' is ordered.

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 is 71%, with the origin/destination/departure/return/currency parameters already documented, including 'omit for anywhere' and the default-currency rules. The description only restates the optionality of destination and dates, adding no format or edge-case detail beyond the schema.

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 — 'cheapest known airfares from an origin city/airport (IATA)' — and clarifies the optional narrowing by destination and month/date. Nothing here overlaps with the eSIM/destination siblings, so the agent can identify it cleanly.

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?

The description implies the use case (price discovery from a known origin) but does not state when to prefer it over, say, search_destinations or when not to use it. With siblings in an unrelated domain, the lack of explicit routing costs little, but it is absent.

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