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

With no annotations, the description carries the full burden and does disclose defaults (omit times → next six hours), that the endpoint is coordinate-bound, and the access mechanics: GET, $0.02 via x402, plus a docs link. It stops short of describing the response payload beyond 'rain probability and expected conditions' or any rate/limit behavior.

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?

Front-loaded with the user-facing question, followed by a compact how-to and a provenance/pricing footer. The first two sentences overlap somewhat ('Will it rain...' / 'Event-window weather odds for San Francisco'), a minor redundancy, but nothing else is wasted.

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?

No output schema or annotations exist, so the description must cover returns and access — it names the returned quantities, the defaults, and the payment/docs route. It could say more about the shape of the returned probabilities (granularity, timezone of timestamps), which is the only remaining gap for a two-optional-param read endpoint.

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 both parameters already document ISO-8601 format, defaults, and the ≤12h span. The description only restates the omit-for-six-hours default, adding no syntax or edge-case meaning (e.g. timezone handling, whether the window can be in the past) 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?

Opens with a concrete question ('Will it rain in San Francisco during your event window') and names the resource, location, and output (rain probability and expected conditions across the window). The line 'Same shape as /v1/forecast/window with the San Francisco coordinates built in' explicitly separates it from the generic window sibling and implies difference from the point-forecast siblings.

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?

States the operational condition clearly ('pass a start and end time (or omit them for the next six hours)') and frames the intent as 'built for scheduling decisions'. It does not, however, tell the agent when to prefer this over weather_forecast_san-francisco or weather_forecast-probabilistic, so there is no explicit exclusion.

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