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

With no annotations, the description carries the full burden of behavioral disclosure. It only explains hostname splitting but does not disclose what happens when other parameters (url, json, path, etc.) are supplied—whether they are ignored, validated, or discarded. The schema's per-parameter notes (e.g., 'discarded after the shape check') are not reflected in the description, leaving a significant gap.

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, concise sentence that front-loads the primary action ('Split a hostname into labels') and immediately adds a clarifying exclusion. No unnecessary words.

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 9 parameters and no annotations or output schema, the description is grossly incomplete. It covers only one input type (hostname) and says nothing about the tool's behavior with URLs, JSON, timezones, or search queries, nor about return values or error handling. An agent cannot determine when to call this tool versus its many siblings.

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 each parameter is already documented. The description adds no parameter-specific meaning beyond mentioning 'hostname' generically; it does not clarify how the 'host' parameter is used or how other parameters relate to the tool's core action. It stays at the baseline for high schema coverage.

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 clarifies it excludes WHOIS/ownership data. However, the input schema accepts nine unrelated parameters (url, json, city, zone, etc.) that the description ignores, making the tool's actual scope ambiguous and failing to distinguish it from sibling shape-checking tools like 'validate-json' or 'browser-url-ok'.

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 on when to use this tool versus alternatives. The description does not mention that for URL validity one should use 'browser-url-ok' or that for JSON validation 'validate-json' is appropriate. The only hint is 'without WHOIS or ownership data', which is a limitation, not a usage criterion.

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