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

With no annotations present, the description carries the full burden of behavioral disclosure. It only adds one negative behavioral fact (no WHOIS/ownership data) and implies no external enrichment, but it does not mention what output the tool produces, whether it is side-effect free, or how it treats the other 8 input parameters. It also fails to reconcile the hostname-only behavior with the entire parameter set.

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 one short sentence with no wasted words and places the main action first. It is under-specified for the tool's actual breadth, but conciseness itself is strong for the hostname-focused interpretation.

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 a complex 9-parameter tool with no output schema and no annotations, a one-sentence description about hostname splitting is far from complete. It does not explain the intended use of these other fields, what the tool returns, or how the shape check works, leaving a roughly adequate agent to guess which input to provide.

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 already covers all 9 parameters with descriptions (100% coverage), so the description does not need to repeat them. However, the general description provides no additional meaning about how parameters relate or which ones are intended for the hostname operation; it only mildly implies 'host' is the main one. This is exactly the baseline 3 situation where the schema does the heavy lifting.

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') and a scope ('without WHOIS or ownership data'), which gives some indication of the tool's core function. However, it does not align with the input schema's 9 optional parameters covering URLs, cities, feeds, JSON, paths, zones, and queries, so it reads as a narrow hostname tool while the schema implies a broader shape-checking utility. It only implicitly distinguishes from siblings like github-repo-shape by the word 'hostname'.

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 any of its 25 siblings, nor any mention of when not to use it. The single line does not name alternatives or give decision criteria.

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