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

The description adds a meaningful behavioral limitation ('without WHOIS or ownership data') and frames the operation as purely lexical splitting. However, with no annotations, it carries the full transparency burden; it does not disclose that most schema inputs are discarded, how invalid hostnames are handled, or any side-effect/permission expectations.

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?

A single compact sentence with no filler, front-loaded with the core action and the main behavioral exclusion. It earns its place and is easy to parse quickly.

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?

There is no output schema or annotations, and the description is too terse for a tool whose schema contains seven unrelated fields and whose family includes several shape/URL siblings. Missing return format, normalization rules, which parameter to populate, and any guidance on when to prefer this over siblings leaves the agent underequipped.

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 schema covers all seven parameters with descriptions, so the baseline is 3, but the description itself adds no parameter-level meaning and never names 'host' as the relevant input. Since there is no required field, the mismatch between the declared hostname focus and the many unrelated optional inputs makes correct invocation ambiguous.

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 uses a specific verb ('split'), resource ('hostname'), outcome ('labels'), and an explicit negative scope ('without WHOIS or ownership data'), so the core action is clear. It does not, however, distinguish it from sibling shape tools like github-repo-shape or figma-url-shape, and the schema lists seven unrelated optional inputs that muddy the declared purpose.

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 given about when to use this tool versus normalize-url, github-repo-shape, or other siblings. The only implied context is the hostname subject, but there are no explicit when/when-not conditions, prerequisites, or alternative tool mentions.

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