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

Annotations already establish read-only, idempotent, non-destructive, open-world behavior. Description adds value by stating 'No auth — US Gov public domain' and noting data coverage 'through the most recent quarter'. No contradiction with annotations. Additional context beyond annotations but not exhaustive (e.g., pagination behavior not mentioned, but schema handles limit).

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?

Five sentences, each serving a purpose: purpose, filtering options, data scope, source attribution, authorization status. No redundancy or filler. Front-loaded with the core function, then specifics.

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 an output schema present and annotations covering safety, the description provides all necessary context: what data is returned, how to filter, data freshness, source, and auth. Nothing essential is missing for an agent 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?

Input schema provides 100% coverage with detailed descriptions: year format examples, limit range, IATA code examples. The description repeats some of this (filter examples) but adds no new semantic meaning beyond the schema. Baseline 3 is appropriate since 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?

Description clearly states the verb ('Query'), resource ('T100 airline segment statistics'), and specific data fields (passenger counts, departures, seats, load factor, payload). It distinguishes from siblings like bts.borders.crossings and bts.freight.indicators by focusing on aviation traffic by airport.

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?

Provides clear context for when to use: US commercial airport traffic statistics, with filtering by airport and year/period. Does not explicitly name alternatives or exclusions, but the domain is distinct enough that an agent can infer applicability. Missing explicit 'use this instead of X' guidance, but the purpose is unambiguous.

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