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

Annotations already cover read-only, non-destructive, open-world behaviour, so the description only needs to add context — and it does: it discloses plan-tier gating (ozone, toxic gases, EPA/DEFRA indices and AQI are paid-plan fields) and a concrete cost of 10 credits. That is genuinely useful pre-call information an agent cannot get from annotations or 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?

Two sentences that are front-loaded on what is measured and what extra fields paid plans unlock, ending with the credit cost. Slight waste in the redundant 'Air Quality: Air Quality is an air pollution API' opening, but otherwise tight.

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?

An output schema exists, so return values need no explanation, and annotations carry the safety profile; the description supplies the plan-gating and cost context. The remaining omission is the no-argument case (what happens if neither city nor zip is given) and whether the data is current-only.

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 schema already documents city, zip and the aqi flag; baseline 3 applies. The description adds only the loose notion that location is 'any city or zip code', and notably with 0 required parameters it never says that at least one of city/zip must be supplied — a gap the schema does not close either.

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 resource and output (particulate pollution levels, PM2.5/PM10 concentrations, health recommendations) for a city or zip code. It is clear what the tool returns, but it never names or contrasts with the obvious neighbours (Weather, WeatherAlerts, ZipCodesLookup), so sibling differentiation is only implied.

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?

The phrase 'check current air conditions' implies when to use it, but there is no explicit when-not guidance and no pointer to alternative tools for weather/forecast data. An agent must infer that this is the pollution-specific lookup rather than a general weather call.

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