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

Annotations already declare readOnly/idempotent/non-destructive, so safety is covered; the description adds value by disclosing the auth prerequisite (EPA AQS email + key) and the nature of the returned content (certification status behind each statistic). It stops short of pagination/rate-limit behavior, but the auth requirement is genuinely useful context not present in the annotations.

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?

Four short sentences, front-loaded with the resource and its outputs, then context and the auth requirement. Slight redundancy between 'EPA AQS annual summary' and 'Sourced from the EPA Air Quality System', but no real waste.

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, no-output-schema read tool, the description covers what is returned, the analytical purpose, and the auth requirement. The return-value enumeration compensates for the missing output schema; only routing among sibling AQS tools is left implicit.

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% with rich per-parameter descriptions (by, bbox, cbsa, site, bdate/edate, limit, param, _apiKey), so the schema does the heavy lifting. The description only references 'a pollutant and area' generically and adds no syntax or constraint detail beyond 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?

States a specific verb+resource: annual summary statistics for a pollutant and area, and even enumerates the statistics returned (mean, max, percentiles, exceedance counts, completeness, certification). An agent can distinguish it from aqs_sample_data and aqs_monitors by the 'annual summary' framing, though no sibling is named explicitly.

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?

Usage is implied rather than stated: 'This is what attainment and trend statements are built on' hints at the analytical context, but there is no explicit when-to-use, when-not, or alternative (e.g., aqs_sample_data for raw observations). An agent must infer the routing.

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