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

Annotations only declare readOnly and openWorld; the description goes well beyond them by disclosing coverage gaps where JMA's feed could not be read, the 30-day window with clamping behavior, and the full record contents (issue/transmission/fetch times, status categories, bulletin URL, SHA-256). These are material traits an agent could not infer from the annotations or schema.

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?

Four tight sentences with no filler: question-form scope first, contents second, window constraint third, routing/negative framing last. Every sentence carries information the agent needs.

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?

An output schema exists, so return values need no explanation, and the description still covers routing, the time window, and data-quality caveats. Nothing an agent needs to select or invoke this tool correctly is missing; the 'see history_window' pointer is a minor loose end but not a blocker.

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 coverage is 100%, so the schema already documents area, since, until and limit thoroughly (formats, defaults, ranges), which sets the baseline at 3. The description adds one genuinely new parameter behavior the schema does not state: that an earlier 'since' is clamped, which affects how the caller should interpret a query.

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 opening sentence states a precise verb+resource+scope: which archived JMA prefectural forecast issuances exist for an area within a time range, and it enumerates exactly what each record contains. It is immediately distinguishable from forecast_as_issued, which the description explicitly routes content requests to.

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 names the alternative (forecast_as_issued) and the condition that selects it ('Use forecast_as_issued for the content'), plus states the 30-day free window and that earlier 'since' values are clamped. 'An archive, not a forecast service' is an explicit when-not statement.

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