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

Annotations already declare readOnly/idempotent/openWorld/non-destructive, so the safety profile is covered. The description still adds non-obvious context: the EPA AQS credential requirement, the data provenance, and the important distinction that this is the quality-assured archive rather than live AQI. It stops short of describing pagination or return row shape.

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?

Three tight sentences, front-loaded with what the tool returns, then why it is authoritative, then the auth prerequisite. Every sentence earns its place; 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?

For a 12-parameter read tool with no output schema, the description covers provenance, authority, auth requirements, and geographies; pagination/limit behavior is the only mild gap, and limit semantics are documented in the schema.

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 parameter meaning is fully carried by the schema (including the same-calendar-year constraint and param code examples). The description adds no parameter-level detail beyond what the schema already states, which is the expected baseline when the 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?

States a specific verb+resource and scope: 'Raw measured air-pollutant sample values from EPA AQS for a date range', plus the geographic grouping (site/county/state/CBSA). It also carves out a clear identity versus a sibling concern ('not the provisional real-time AQI'), so an agent can distinguish it from aqs_annual_summary/aqs_monitors without opening schemas.

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?

Gives an explicit selection rule: use this as the AUTHORITATIVE, quality-assured archive when you need actual concentrations on specific dates, as opposed to provisional real-time AQI. It does not, however, name the sibling tools (aqs_annual_summary, aqs_monitors) or say when to prefer them, so routing among the AQS family is left to inference.

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