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

Annotations already declare readOnlyHint=true and openWorldHint=false, so the safety profile is covered. The description adds genuinely useful behavioral context by bounding coverage to the contiguous US or Australia and identifying the GFS model, which tells the agent calls outside that geography will fail. It says nothing about units, timezone of the hourly timestamps, or failure modes.

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 front-loaded sentence that names the model, granularity, variable set, and geographic scope with no filler. Nothing is padded and the most decision-relevant facts come first.

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 does list the returned variables, which is the right move. However, for a three-parameter tool with zero schema coverage it omits the hours semantics, output units, and timestamp timezone — gaps an agent must guess at to invoke 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 0%, so the description carries the burden, and it does not compensate. 'For a point' loosely implies lat/lon, but the hours parameter — with a default of 48 and a hard ceiling of 120 — is never mentioned, leaving the agent to discover the range and default from the raw schema alone.

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 resource and resolution — 'Hourly GFS forecast' — and enumerates the returned variables (temperature, humidity, wind, gust, precipitation, cloud), which implicitly separates it from the daily and current-conditions siblings. It stops short of explicitly naming those siblings, but the verb+resource+granularity combination is clear enough to select on.

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: 'hourly' suggests picking this over weather_forecast_daily when hour-level resolution is needed, and the geographic scope hints at when the call will succeed. There is no explicit statement of when to prefer this over weather_current or weather_forecast_daily, and no prerequisite guidance.

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