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 meaningful traits: the default window behavior, what is returned (rain probability and expected conditions), the HTTP GET transport, and notably that the call costs $0.02 via x402 (a payment/auth requirement). It omits error behavior, rate limits, and freshness/latency details.

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 description is front-loaded with the core question and keeps prose tight; the bracketed endpoint/price/docs metadata is dense but informative. Slightly redundant between the opening question and the second sentence's restatement.

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 state what comes back (rain probability and expected conditions across the window), and it covers cost, transport, and docs. For a two-optional-param read tool this is nearly complete; only error/edge-case behavior is unaddressed.

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 start/end formats, the ≤12h constraint, and defaults are already documented in the schema. The description adds only the 'omit both for the next six hours' framing, which largely restates the schema defaults — baseline 3 is appropriate.

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 names a specific verb and resource (event-window rain probability for Phoenix) and explicitly relates itself to the generic sibling ('Same shape as /v1/forecast/window with the Phoenix coordinates built in'), so an agent can separate it from weather_forecast-window and weather_forecast_phoenix without opening any 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?

It gives clear usage context ('built for scheduling decisions') and states the default invocation path (omit start/end for the next six hours), plus a comparison to the base /v1/forecast/window tool. It stops short of explicit when-not-to-use guidance against the point-forecast or probabilistic siblings.

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