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

The annotation readOnlyHint=true is consistent with the description, which describes an opening of a widget (a read-like UI action). The description adds context about the WKT being usable in other tools, but does not disclose details such as user interaction requirements or result delivery (e.g., whether the WKT appears in the UI or is returned). Given annotations cover the safety profile, a 3 is appropriate.

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?

Two concise sentences: first states what the tool does, second explains its downstream use. No fluff, efficient and complete for the purpose.

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 zero-parameter UI-opening tool with a readOnlyHint annotation, the description adequately explains its function and relevance to sibling analysis tools. It does not specify return value or UI behavior, but these are not critical for an agent to invoke the tool correctly given its simple nature.

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?

The tool has zero parameters and the schema coverage is 100% (empty schema). Per calibration, 0 params earns a baseline of 4. The description adds no parameter details because none exist, which 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 states a specific verb ('開きます' - opens) and resource ('ポリゴンを描画し、WKT POLYGON文字列を取得するウィジェット'), clearly distinguishing this from all sibling analysis tools. It explains what the tool does and what output it provides.

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 by listing sibling analysis tools that can consume the WKT output, indicating when this tool is useful as a prerequisite. However, it does not explicitly state when not to use it or mention alternatives, as there are no direct alternatives among siblings.

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