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 adds 'without WHOIS or ownership data,' which warns about an external data dependency that does not happen. However, it does not state whether this tool is read-only, what it does with the input, whether it makes network calls for other parameters, or how it treats the 'discarded' fields. The description's one trait is a useful boundary, but it is not enough for a 9-parameter tool without any annotation.

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 sentence is short and front-loaded, but for a tool with nine heterogeneous parameters, the description is under-sized—it leaves out the global purpose and the parameter usage context. Compared to a simple tool, a single cryptic sentence is not 'appropriately sized'; it is an under-specification rather than concise efficacy. There is no remove overhead, but it does not contain the needed structure, warranting a mid-range 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 the complexity (9 parameters, none required, no output schema, no annotations), the description output is far from complete. It does not explain how to invoke the tool (which parameter, whether any can be used in parallel, whether some are mutually exclusive), what the return shape looks like, or what 'split' means as a call to it. The agent cannot reliably use this tool on its own from the provided text.

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 reported as 100%, so all parameters have descriptive descriptions that clarify their use (e.g., 'ref' is 'discarded after the shape check', 'host' is 'public hostname'). The tool description adds no additional parameter semantics beyond the schema, so the baseline of 3 applies. It does not need to repeat the schema, but it could have tied the 'host' parameter to the described splitting behavior, which it does not.

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 claims a specific action—'Split a hostname into labels'—but the input schema includes url, city, feed, json, path, zone, query, and ref. This suggests the tool is actually a general purpose 'shape checker' for many kinds of inputs, but the description does not reveal that broader purpose. An agent reading the description would expect this tool only handles hostnames, which contradicts the other parameters and may lead to incorrect selection.

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 gives no guidance about when to use this tool relative to siblings like figma-url-shape, github-repo-shape, or jira-key-shape. It also does not mention which parameter to pass for which task, even though the schema offers nine disjoint optional inputs. There is no indication of when to use one parameter over another, nor exclusions for wrong use.

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