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

With no annotations, the description must disclose behavioral traits. It only mentions hostname splitting and the absence of WHOIS/ownership data, but says nothing about how the other parameters (city, feed, json, zone, query, etc.) are handled or what side effects occur. The schema descriptions like 'discarded after the check' hint at validation behavior, but the tool description does not unify this.

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, grammatically simple sentence that front-loads the core action and limitation. It is concise with no filler, but it omits the tool's full parameter surface, which undermines its utility despite its brevity.

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 nine optional parameters, no output schema, and no annotations, the description is severely incomplete. It only covers hostname handling and provides no information about the behavior for the other eight parameters, error cases, or return values. An agent cannot reliably predict what this tool does with most inputs.

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 provides 100% coverage with per-parameter descriptions, but the tool description adds no meaning beyond that. More critically, the description's focus on hostname conflicts with the wide array of parameters, creating confusion about the tool's actual scope. The description fails to explain how parameters relate to the stated purpose.

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 ('Split a hostname into labels') and a clear limitation ('without WHOIS or ownership data'), which distinguishes it from sibling shape tools like github-repo-shape and jira-key-shape. However, the input schema contains nine unrelated parameters (ref, city, feed, json, etc.), so the description only covers a fraction of the tool's apparent behavior.

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 on when to use this tool versus alternatives such as normalize-url, browser-url-ok, or the other shape tools. The description does not mention prerequisites, exclusions, or preferred contexts, leaving the agent to infer applicability.

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