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

Annotations already declare readOnlyHint=true, openWorldHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is fully covered. The description adds valuable behavioral context: the maximum query range (~1 year per call), the data availability start date (2022-01-01), the data source (Copernicus CAMS reanalysis), and the licensing (CC BY 4.0). It also notes 'no auth', which is useful for an agent deciding whether it can call this tool directly.

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 compact and information-dense. Every sentence earns its place: the first states the core function, the second lists the return content, the third gives the data availability window, the fourth states the query range limit, and the fifth covers data source, auth, and licensing. It's front-loaded with the most important information and has no filler.

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?

The description is complete for a read-only data retrieval tool. It covers the data source, availability window, query range limit, auth requirements, and licensing. The output schema exists, so return values don't need to be explained in the description. The only minor gap is that it doesn't explicitly mention the timezone parameter's effect on returned timestamps, but the schema already covers that.

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 all 6 parameters thoroughly. The description adds a bit of context by listing the available pollutants and mentioning the default set, which complements the schema's pollutants parameter description. However, it doesn't add significant meaning beyond what the schema already provides for latitude, longitude, start_date, end_date, and timezone. 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?

The description states a specific verb ('Retrieve'), a clear resource ('hourly historical air quality data'), and a scope ('for a date range at any global location'). It lists the returned pollutants and distinguishes itself from sibling tools like openmeteoaq.air.current and openmeteoaq.air.forecast by explicitly saying 'historical'.

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 clearly indicates when to use this tool: for historical air quality data over a date range. It mentions the data source (Copernicus CAMS reanalysis) and the availability window (from 2022-01-01), which helps an agent decide if this tool is appropriate. It doesn't explicitly name alternatives like openmeteoaq.air.current or openmeteoaq.air.forecast, but the 'historical' qualifier and the date-range focus make the usage context clear.

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