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 states 'No browser is launched,' which is a minor safety note. It does not explain why the schema includes parameters like city, json, path, or zone, nor what happens with them (the schema hints at 'discarded after...' but the description omits this). The description also fails to mention any side effects, permission requirements, or return format. For a tool with 9 optional parameters, this is a significant transparency 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, front-loaded sentence with no wasted words. It efficiently conveys the core action and a key behavioral caveat. However, given the tool's complexity (9 parameters, multiple potential uses), the extreme brevity may under-specify the tool's actual capabilities, though that is more a completeness issue than a conciseness one.

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 optional parameters, no output schema, and no annotations. It does not explain what happens with non-URL parameters, what the return value indicates, or how the tool relates to its siblings. An agent would struggle to call this tool correctly without examining the schema in detail, and the description does not resolve the obvious mismatch between its stated purpose and the broad schema.

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 the baseline is 3. The description adds no parameter-level information beyond what the schema already provides; it only mentions 'URL' generically. While it does not need to repeat the schema, the description does not help an agent understand why parameters like city, json, and path exist for a URL-checking tool. This mismatch is not the description's job to resolve fully, but it fails to add any semantic value to the parameters.

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 clear verb and resource: 'Check whether a URL can be opened.' This distinguishes it from siblings like normalize-url (which normalizes) and fetch-status (which fetches). However, the input schema includes many non-URL parameters (city, json, path, etc.), which creates ambiguity about the actual scope of the tool. The description itself is unambiguous about its primary function, so a 4 is appropriate.

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 gives no guidance on when to use this tool versus alternatives. It does not mention any conditions, exclusions, or reference to sibling tools. An agent has no indication of when to pick this over fetch-status or normalize-url, leaving the decision to inference.

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