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

No annotations exist, so the description carries the full burden. It discloses one behavioral trait (no WHOIS/ownership lookup) but says nothing about return values, side effects, or how parameters like json ('discarded after the check') behave; the only behavioral detail about json lives in the schema, not the description.

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, front-loaded sentence with no filler. The negative qualifier is informative and earns its place.

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?

For a tool with four heterogeneous optional parameters, no annotations, and no output schema, this one-liner is insufficient. It does not explain how url, json, and zone relate to the stated purpose, nor what an agent should expect as a result.

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 documents all four parameters with descriptions, so the baseline is 3. The tool description adds no parameter-level meaning and even creates ambiguity by describing only hostname splitting while the schema also accepts url, json, and zone.

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 an explicit exclusion ('without WHOIS or ownership data'), which distinguishes it from ownership-enrichment tools. However, the input schema accepts four unrelated parameter types (url, host, json, zone), so the description only covers part of the tool's apparent surface area.

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 choose this tool over alternatives. The negative clause 'without WHOIS or ownership data' hints at a use case but does not state contexts, prerequisites, or exclusions.

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