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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint, so the safety profile is handled. The description adds useful behavioral detail: ranked results, no connection logic, and the empty-result semantics. It does not contradict the annotations, though it does not discuss anything like pagination or limits beyond the 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?

The description is compact and front-loaded: use cases first, then mechanics, then the alternative tool. It loses full marks because the 'both origin and destination are required' statement sits uneasily against the 'touching an airport' behavior and the origin-only example, slightly muddying an otherwise efficient structure.

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 still explains what is returned (flight numbers ranked by probability) and what an empty result means. The main gap is the unresolved destination-optionality question around 'touching an airport' and 'what Starlink flights serve airport X?', which an agent would need clarified to use the tool reliably in all described cases.

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 100%, so the baseline is 3; the description adds the important context that origin and destination are both required for route comparison. However, this conflicts with the schema's required-parameter count of 0 and the origin-only example, which creates genuine ambiguity for an agent deciding what to pass.

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?

Clearly identifies the resource and behavior: a single-route lookup returning tracked airlines' flight numbers ranked by Starlink probability. It also explicitly names the key sibling alternative, plan_starlink_itinerary, while the route-vs-itinerary distinction is concrete enough to prevent confusion.

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?

Gives explicit trigger examples ('which flights between X and Y have Starlink?'), an explicit exclusion ('no connection logic or coverage-ratio ranking'), and an explicit alternative tool recommendation for connection planning. It also tells the agent what an empty result means, which is practical guidance for interpreting the response.

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