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

Annotations cover the safety profile (readOnlyHint, openWorldHint), so the bar is lower, and the description still adds real behavioral context: the data source ('nearest active monitor'), the 365-day range cap, and the paid-per-call cost ($0.003 USDC via x402), which is critical for an agent deciding whether to invoke it. It does not mention failure modes when no monitor exists nearby.

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?

A single dense sentence front-loads the resource and scope, followed by the pricing note. Every clause carries information (metrics returned, pollutants, source, range, cost), with 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?

With no output schema, the description usefully enumerates the returned fields, and it discloses cost and data provenance for a 5-parameter, no-required-param tool. The remaining gap is the unexplained relationship between the 'near' place name and lat/lon coordinates, which matters for correct invocation.

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 60%; lat/lon carry no schema description. The description adds the pollutant vocabulary (PM2.5, PM10, ozone, NO2, SO2, CO) that maps to the 'parameter' field, but it never clarifies that 'near' and lat/lon are alternative location selectors or how they interact. Baseline 3 given partial schema coverage.

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 (returns history) and resource (air pollution data) and even enumerates the returned metrics (daily avg/min/max, US AQI, worst day, WHO exceedance days, trend). It distinguishes itself from a current-conditions tool only implicitly via 'history' — it never names siblings like airquality, airquality_compare or airquality_stations.

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 only implied: 'history ... up to 365 days' suggests retrospective analysis versus the sibling airquality for current readings, but there is no explicit when-to-use, when-not-to-use, or alternative-routing sentence. An agent must infer the choice from the tool name.

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