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

Annotations already declare readOnlyHint=true, destructiveHint=false, and openWorldHint=false, so the safety profile is covered. The description goes further by describing the analytic output ('dead legs', 'hub routing fixes', 'proven carrier combinations'), which no structured field provides since there is no output schema. It stops short of explaining result format or whether 'dead leg' is rendered as a boolean, list, or verdict.

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, zero filler, and the core action is front-loaded before the diagnostic details. Efficient and readable; only the trailing geographic clause is somewhat loose and could be tightened.

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 a read-only diagnostic tool with 100% schema coverage and no output schema, the description supplies the missing piece: what the analysis actually yields (dead legs, hub fixes, carrier combos). An agent can decide to call it and know roughly what comes back. It lacks a note on whether this substitutes for or complements fare_quote/route_validate.

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 100%: from/to IATA codes and the optional alliance preference are fully documented in the schema with examples. The description adds no parameter-level meaning such as valid alliance values beyond 'star'/'oneworld' or how alliance interacts with hub selection. Baseline 3 applies 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 gives a specific verb+resource ('Check the best connection between two airports') and then enumerates concrete outputs: dead-leg identification, hub routing fixes, and carrier combinations. That is far more informative than the bare name. It never names or contrasts a sibling (route_validate, route_suggest, plan_route), so it stops short of the top score.

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?

'Essential for transpacific, kangaroo, and intra-Asia routing' gives geographic context for when the tool matters. However, it offers no when-not conditions, no prerequisites, and no explicit routing to alternatives among the many route/fare siblings. Usage is implied rather than prescribed.

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