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

Annotations already declare readOnlyHint=true, so the safety profile is covered. The description adds genuinely useful operational context beyond that: ~7-day retention per station, roughly 5-minute reporting cadence at busy airports yielding 100+ observations per day, and an assurance that paging neither repeats nor skips observations. It does not mention rate limits or error behavior, keeping it short of a 5.

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 the core purpose before retention, volume, and paging details. Every clause carries operational information; nothing is filler or repetition of the tool name.

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, return-value documentation is unnecessary, and the description covers everything else an agent needs: how to obtain a station ID, how far back data reaches, expected data volume, and full pagination mechanics.

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 baseline is 3, but the description adds semantic constraints the schema doesn't spell out as directly: start is inclusive, end is exclusive, and nextCursor drives backward paging. It does not restate limit bounds or the cursor's opacity, which the schema already covers.

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 and resource (recent observation history for a station, newest first) and explicitly differentiates itself from the sibling nws_get_observations by framing the result as 'the trend behind the single latest reading' that sibling returns. An agent can pick between the two without opening either schema.

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 explicit when-to-use conditions (trend analysis vs. a single reading), names the discovery alternative (nws_find_stations to get a station ID near a coordinate), and explains how to narrow (start/end) and how to page back (nextCursor). No alternatives are left to inference.

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