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

Annotations already declare read-only, idempotent, non-destructive and closed-world, but the description adds substantive context beyond them: data source (METAR VTSP, Iowa Environmental Mesonet archive), the returned time window (last full month plus past-year average), a data timestamp, and a source URL that may be a month page or JSON. That is rich operational detail not derivable from 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?

The trigger condition is front-loaded and every element (returns, source, timestamp, contrast with forecast and climate) earns its place. The prose is a dense run-on sentence rather than cleanly separated points, which slightly hurts scannability.

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?

There is no output schema, so the description carries the burden and does so well: it explains the return content, comparison to normal, data timestamp, and the URL/page-vs-JSON behavior. An agent has everything needed to call it correctly.

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% and the single 'month' parameter is already well documented (1=January, 9=September, returns the last complete such month). The description echoes the 'latest matching month' semantics without adding format or edge-case detail beyond the schema, so the baseline of 3 applies.

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+resource: it returns observed weather (rainy days, thunderstorms, long daytime rains) for the latest matching month on Phuket, plus the multi-year average. It explicitly distinguishes itself from siblings by naming get_climate and by declaring it is a past fact, not a forecast.

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?

It gives an explicit trigger ('Вызывайте, если спрашивают, как было на самом деле...') and names the alternative for climate norm (get_climate). It does not explicitly rule out get_weather_now for current conditions, so the boundary with that sibling is only implied.

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