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

With no annotations, the description carries the full burden and discloses that this is an HTTP GET endpoint, costs $0.02 via x402, and links to docs. It also describes the returned content (rain probability and expected conditions) and references a sibling endpoint shape, though it omits rate limits, exact response format, and authentication details beyond the payment protocol.

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 purpose and uses a compact structure, with the pricing and endpoint metadata confined to a final bracket. The opening rhetorical question and subsequent restatement of the same event-window scope introduce slight redundancy, preventing a perfect score.

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?

Given two optional parameters, rich schema descriptions, and no output schema, the description gives enough for an agent to invoke correctly: it explains the window concept, defaults, returned content, cost, and docs. Return-value details remain vague and the 12-hour window cap is only in the schema, but the essential invocation context is covered.

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 both parameters are already documented with formats, defaults, and constraints. The description adds limited value beyond the schema by noting that start and end can be omitted for the next six hours, which largely restates the schema defaults.

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 (get rain probability and expected conditions), resource (weather forecast), and scope (San Antonio, event window), and distinguishes itself from the generic window forecast by noting the San Antonio coordinates are built in. An agent can tell it apart from city-specific point forecasts and generic window forecasts without opening the 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?

The description provides clear context for when to use it: event-window forecasting for scheduling decisions, with optional start/end and a default omission for the next six hours. It mentions the generic /v1/forecast/window shape as a comparison, but does not explicitly name alternatives or state when not to use this tool.

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