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

Annotations already declare the safe read-only, idempotent profile, and the description adds substantial context on top: the list is a curated catalogue (six featured routes, then top searches over 30 days), served from a cache refreshed roughly every 30 minutes, so results are stable rather than a live ranking. It also defines the minPrice field's exact scope and its null semantics, which the annotations cannot convey.

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?

Purpose is front-loaded in the first clause and every sentence carries information: field definition, stability guarantee, cache behavior, and the handoff. It is a dense single paragraph with one long embedded clause, but nothing is padding.

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 carries the burden of explaining return values and does so fully, including units (USD), tax handling (shown at checkout), and the null case for missing prices. An agent can call this and interpret the result without further information.

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?

The tool takes no parameters, so the baseline is 4. The description describes the response fields (origin, destination, minPrice in USD, null when unlisted), but there is no input to characterize further.

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 ('List popular SkyAccess private jet routes') and enumerates exactly what each entry contains (origin, destination, minPrice). It is clearly separable from search_empty_legs, whose role is explicitly handed off at the end.

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 closing sentence 'Pass a route to search_empty_legs to see its flights' tells the agent precisely what to do next once it has a route, which is genuine routing guidance. It lacks an explicit when-not statement (e.g. when to skip straight to search_empty_legs if a route is already known), so it falls short of a full 5.

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