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

The description discloses that the tool does not return WHOIS/ownership data, which is a behavioral limitation. Yet no annotations are provided, so the description carries the full burden. It does not mention return format, mutations, persistence, or side effects; some of this is hidden in schema descriptions (e.g., 'discarded after', 'no disk access'), but the tool description itself stays largely implicit.

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, efficient sentence that front-loads the core action and immediately provides a meaningful limitation. No redundant words; every element adds information.

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?

The tool has nine optional parameters and no output schema, so the description should explain what the tool does with all of them and what kind of result it produces. The current text only covers the hostname case and leaves callers to guess whether city, path, JSON, query, etc., are accepted and how they relate to the hostname split. This is a significant completeness gap.

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 is already explained in the structured part of the tool. The tool description only reinforces the meaning of the hostname parameter ('split into labels') and does not add semantic nuance to other parameters. This meets the baseline for interaction with rich schema coverage.

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 a specific action on one resource ('Split a hostname into labels') and the negative constraint ('without WHOIS or ownership data'). It distinguishes this tool from siblings like github-repo-shape or jira-key-shape. However, the input schema lists nine non-hostname parameters, so the description does not fully reflect the tool's apparently broader input surface.

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 phrase 'without WHOIS or ownership data' implies a use case where the agent only needs host labels and not ownership enrichment. It does not, however, mention alternatives or give an explicit 'use this when...' guidance that would help the agent pick this tool over sibling shape tools or other URL utilities.

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