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 does disclose that page content is not stored, which is a meaningful side-effect note. However, it doesn't mention whether the tool makes network requests, handles redirects, or any error/edge-case behavior. This is minimal but not entirely absent.

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 exactly two sentences with no fluff. It front-loads the primary purpose and adds a single clarifying note. Every word earns its place, making it appropriately concise and well-structured.

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?

The description is incomplete for a tool with 9 parameters. It only explains behavior for URLs, but the schema includes parameters like 'city', 'zone', 'json', and 'feed' that are not addressed. There is no output schema, so the return format is unspecified. An agent would be unclear on what the tool actually does with these other inputs, making the description insufficient for correct invocation.

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 all 9 parameters have descriptions in the schema. The tool description itself adds no extra meaning to the parameters, which is acceptable per the baseline rule. The description does not explain how the many non-URL parameters relate to the stated purpose, but the schema already documents each one.

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 verb ('Return') and resource ('host, scheme, and HTTP status for a URL'), which clearly identifies the core purpose. The note that page content is not stored helps distinguish it from content-fetching tools. However, the tool's schema includes many non-URL parameters, so the description doesn't convey the full scope of the tool's functionality.

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?

The description provides no guidance on when to use this tool versus sibling tools like fetch-status or normalize-url. It doesn't mention any specific conditions or alternative tools, leaving the agent to infer usage from the schema alone.

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