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

Annotations already declare readOnly/idempotent/non-destructive/openWorld, so safety is covered. The description adds genuinely useful behavior beyond them: overflow rows surface as truncated/total_matching rather than being silently dropped, and unknown carrier/airport codes fail with a clear error instead of an empty success. It stops short of return-shape or auth/rate-limit details, keeping it at a strong 4.

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 front-loaded with what it returns, then usage, then pagination/error behavior — a sensible order with no filler sentences. It is somewhat dense with em-dashes and parentheticals, but each clause carries actionable information.

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 enumerates the returned field categories, and it covers scoping, pagination, truncation signaling, and error semantics for the two optional filters. Alongside present annotations and 100% schema coverage, an agent has everything needed to call it correctly.

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 schema already documents year, limit, offset, airport, and carrier, including the carrier code-or-name flexibility. The description's mentions of carrier/airport scoping and limit/offset paging restate the schema rather than adding syntax or format detail, so the baseline 3 is appropriate.

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 — delay-cause rows for a given year from BTS TranStats on-time data — and enumerates the returned measures (arriving flights, 15+ minute-late arrivals, cancellations, diversions, delay minutes by cause). It explicitly contrasts with the sibling bts_airport_delays, explaining the difference is organization (year-first vs airport-first), so an agent can route 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?

Gives explicit when-to-use cases ('scan a whole year across carriers/airports, or to compare one carrier's delay profile across the airports it serves') and pairs them against the alternative tool by describing the contrasting shape. It also tells the agent how to proceed when results are too large (narrow with carrier/airport or page with limit/offset).

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