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

No annotations are provided, so the description carries the full burden. It does not disclose that data is discarded, that there is no WHOIS/ownership lookup, that no disk access occurs, or what the tool actually returns. The schema hints at 'shape check' behaviors, but the description omits any behavioral details, leaving the agent in the dark about side effects and output.

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 sentence, which is concise, but it is under-specified for a tool with 9 parameters. It front-loads only one aspect (hostname splitting) and omits the broader purpose. The brevity is not effective because it fails to convey essential 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?

Given the tool's complexity (9 parameters, no output schema, no annotations), the description is severely incomplete. It does not explain what the tool does for the other parameter types, what the result looks like, or how to invoke it correctly. An agent cannot reliably use this tool based on the description alone.

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 coverage is 100%, so each parameter has a description, but the tool description adds nothing beyond the schema. It only mentions 'hostname' while ignoring the other 8 parameters, failing to clarify their roles or how they relate to splitting a hostname. The schema descriptions like 'discarded after the shape check' are ambiguous, and the description does not compensate.

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 'Split a hostname into labels' which is a specific verb+resource, but the input schema includes 9 unrelated parameters (ref, url, city, feed, json, path, zone, query) that are never mentioned. This creates ambiguity about the tool's actual scope and misleads the agent into thinking it only handles hostnames. It is not a tautology, but it is vague and incomplete for the actual tool 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?

There is no guidance on when to use this tool versus siblings like normalize-url, file-path-ok, or jira-key-shape. No conditions for selection, no alternatives mentioned, and no exclusions. The agent has no basis to choose this tool over similar shape-checkers.

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