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

Annotations already cover readOnly/idempotent/openWorld, but the description adds real context: the BTS TranStats data source, that unknown carrier codes are refused with a clear error rather than an empty success, and that months caps the most recently loaded months. It doesn't mention rate limits or latency, so not a 5.

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, followed by parameter usage, return shape, and error behavior, with no filler sentences. Slight overlap with schema-documented parameters keeps it from a 5.

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?

No output schema exists, yet the description enumerates the return shape (flights, on-time %, average arrival delay, cancellations, diversions, delay minutes by cause) and covers default behavior, scoping, and error semantics. Nothing an agent needs to call it correctly is missing.

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%, so the baseline is 3. The description's parameter notes (2-letter code or common name, airport scoping, months default 12) largely restate the schema, adding no syntax or format detail beyond it.

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 (monthly on-time performance), a precise resource scope (one airline, aggregated across all routes or routes touching one airport), and names the sibling route_ontime whose shape it mirrors. An agent can distinguish it from route_ontime without opening either schema.

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?

Explains when to pass airport (scope to flights where that airport is origin or destination) and implicitly routes the agent to route_ontime for per-route data by describing this tool as aggregated. No explicit when-not statement or named alternative condition, so it stops short of a 5.

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