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

No annotations are provided, so the description must carry the full burden of behavioral disclosure. It only states a negative ('without WHOIS or ownership data') but does not explain side effects, data handling, or what the tool does with the varied parameters. The schema hints at discarding inputs, but the description itself offers no behavioral context.

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 only one sentence, which is extremely concise, but it is under-specified rather than appropriately sized. It lacks any structure or additional details needed to understand the tool's full behavior, making the brevity a deficiency rather than an asset.

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 nine optional parameters, no output schema, and no annotations, the tool is complex. The description covers only hostname splitting, ignoring the other eight parameters and the overall tool semantics. The schema descriptions partially compensate, but the description leaves critical context missing, such as when to use each parameter or how the tool behaves as a whole.

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%, with each parameter having a description (e.g., 'discarded after the shape check'). The tool description adds no parameter-level meaning beyond the schema, so the baseline of 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?

The description states a specific action—splitting a hostname into labels—and clarifies it excludes WHOIS/ownership data. However, the input schema accepts nine unrelated parameters (e.g., city, json, query) that do not align with hostname splitting, so the stated purpose is incomplete and potentially misleading about the tool's actual scope.

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?

No guidance is provided on when to use this tool versus alternatives. With many siblings like normalize-url, github-repo-shape, and figma-url-shape, the description offers no selection criteria, making it impossible for an agent to choose correctly.

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