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

Annotations already convey a safe, read-only, idempotent operation, so the description does not need to repeat that. It adds meaningful behavioral context beyond annotations by naming the data source (Open-Meteo, CAMS + EPA AirNow blend) and disclosing the exact return payload elements and units, which helps the agent set expectations.

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 a single dense sentence that front-loads the core resource and location mode, then lists return metrics and the source. Every clause adds useful information and there is no filler or redundant repetition of the schema.

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?

Given there is no output schema, the description does well to spell out the main return fields. However, it does not clarify that a location is required even though the schema lists no required parameters, nor does it mention how this tool relates to nearby weather siblings. These gaps make it only moderately complete for an agent deciding how to invoke it.

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 only 33%, so the description carries substantial responsibility. It does clarify that the tool accepts either a lat/lon pair or a US ZIP, which adds meaning beyond the bare schema. Yet it stops short of explaining coordinate format, whether location inputs are mandatory despite zero required parameters, or how conflicts between zip_code and lat/lon are resolved.

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 clearly identifies the resource as current air quality at a location and enumerates specific output types (AQI, pollutants, band, primary pollutant). It is unambiguous next to weather siblings, though it lacks an explicit verb and does not directly name a competing sibling for differentiation.

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 'Current air quality' strongly implies this tool is for present conditions and not forecasts or historical analysis, and the location inputs are stated. However, there is no explicit guidance on when to prefer this over weather_current, weather_forecast, or other weather siblings, and no exclusions are mentioned.

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