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

The description discloses that this is a pure parsing operation and explicitly disclaims WHOIS/ownership enrichment, which is useful. With no annotations present, however, it does not describe return structure, handling of invalid hostnames or trailing dots, or whether any external lookup occurs beyond the disclaimer.

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 sentence that is front-loaded with the action and target, with no filler or repetition. The brevity is concise rather than vague, and the under-specification is a completeness issue rather than a structure issue.

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?

Despite having no output schema and no annotations, the description stops at the input transformation. It does not explain what 'labels' means structurally, how invalid input is handled, or which of the 9 optional parameters should be used. The generic 9-parameter schema makes this omission more serious.

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 the baseline is 3; the schema already documents 'host' as 'Public hostname' and marks the other parameters as discarded/ignored. The description adds no parameter-level meaning and does not explicitly point to which parameter should be populated, but it does not conflict with the schema.

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?

States a specific transformation: 'Split a hostname into labels'. The phrase 'without WHOIS or ownership data' narrows scope and distinguishes it from ownership/WHOIS lookups, though it does not explicitly name a sibling tool.

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 conditional guidance or alternative tool is mentioned. The negative clause 'without WHOIS or ownership data' hints at a boundary, but an agent cannot tell when to choose domain-shape over normalize-url, fetch-status, or the other shape tools. This is effectively no usage guidance.

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