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

With no annotations present, the description carries the full burden and does disclose meaningful operational traits: HTTP GET (read-only), a $0.02 cost paid via x402, and a docs link for more detail. It stops short of describing the response shape or failure modes, but the payment/auth and method disclosure is genuine value that is not present in any structured field.

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 and the core outcome, then the operational bracket. The first two sentences overlap heavily ('Will it rain in San Diego during your event window' / 'Event-window weather odds for San Diego'), which is mild redundancy, but overall it is tightly sized with no filler.

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?

For a two-optional-param, zero-annotation tool with no output schema, the description covers purpose, default behavior, cost, transport, and a docs pointer — enough to invoke it correctly. The main gap is that, absent an output schema, the return payload is only summarized rather than specified.

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 schema already documents both start and end with ISO-8601 format and their defaults. The description only restates defaults loosely ('omit them for the next six hours') without adding syntax or constraint detail beyond the schema's '≤12h after start'. Baseline 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?

States a specific purpose — rain probability and expected conditions for San Diego across a caller-supplied event window — which is concrete and distinguishable from a generic forecast. It also notes it is 'the same shape as /v1/forecast/window with the San Diego coordinates built in,' which separates it from the coordinate-free sibling, though it does not address the other near-twin, weather_forecast_san-diego.

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 implied rather than stated: 'built for scheduling decisions' plus 'omit them for the next six hours' tells the agent when the defaults apply, but there is no explicit when-to-use/when-not guidance and no named alternative for cases where the agent should pick a different weather tool.

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