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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint, so the baseline is lowered. The description adds valuable context: no API key required, global coverage with hourly updates, data source (Copernicus CAMS), and licensing. These go beyond annotations and help the agent understand operational constraints.

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 paragraph that front-loads the primary purpose, then lists outputs, then operational details. It avoids redundancy and stays under 100 words. Slightly long due to the metric enumeration, but every sentence earns its place.

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, the description is free from needing to document return structure. It covers purpose, data source, output metrics, auth, update frequency, coverage, and licensing. Combined with the schema and annotations, an agent has all necessary information to invoke 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 has 100% coverage with detailed descriptions for latitude, longitude, and timezone. The description adds no parameter-specific guidance beyond listing the return metrics, which is already implied by the tool purpose. It does not explain how timezone affects timestamps beyond what the schema says, so it adds minimal value over the schema.

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 states the tool fetches real-time air quality for any global location, and enumerates the specific pollutants and AQI scales returned. This distinguishes it from sibling tools like forecast, historical, and pollen, which are obvious from the tool name and the 'real-time' qualifier.

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 description states it provides real-time conditions, which implies use for current measurements rather than forecast or historical data. However, it does not explicitly reference sibling tools or exclusion conditions, leaving the agent to infer when to choose this over openmeteoaq.air.forecast or .historical. Clear context but no explicit alternatives.

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