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 states the primary operation (splitting) and a limitation (no WHOIS/ownership), but does not describe return format, side effects, error behavior, or what happens with the other eight parameters. The mention of 'discarded' in the schema is not echoed here, and the description is too sparse to be transparent.

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 a single sentence, which is concise and front-loaded with the main action. However, it is so brief that it omits essential context about the schema's breadth and any additional behavior. It is not misleading, but it under-specifies rather than being efficiently complete, so it earns an average 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?

This tool has 9 optional parameters, no output schema, and no annotations, making the description the sole source of context. It fails to explain the purpose of most parameters, the return value, or how the tool behaves in different scenarios. An agent would be completely lost trying to call this tool correctly for anything other than a plain hostname split, and even then the output format is unknown. The description is grossly inadequate for the tool's complexity.

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 each parameter has its own description, which would normally give a baseline of 3. However, the tool description only references 'hostname', implying the 'host' parameter is central, while the schema lists many unrelated parameters. The description adds no meaning about how parameters relate to the stated purpose, and even creates confusion about whether the other parameters are relevant. This degrades the value below the baseline.

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 clearly states the core action: 'Split a hostname into labels' and adds a limitation ('without WHOIS or ownership data'). However, the input schema exposes 9 parameters, most of which (city, feed, json, path, zone, query) have no relation to hostname splitting. This creates ambiguity about the tool's actual scope, so the purpose is not fully clear.

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 on when to use this tool versus alternatives. It mentions 'without WHOIS or ownership data' as a distinguishing factor, but does not name sibling tools like figma-url-shape or github-repo-shape, nor does it state exclusions beyond that single note. An agent cannot reliably decide between this and similar shape-check tools.

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