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 reveal a key behavior ('No browser is launched'), which is useful, but it omits any other behavioral details: what happens with the parameters, side effects, error cases, or response format. A single behavioral note is far from adequate for a tool with 9 parameters and no annotation support.

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 extremely concise, consisting of one sentence with no fluff. It front-loads the core purpose. While its brevity is a strength, it borders on under-specification rather than effective conciseness, but it doesn't waste words or include irrelevant details.

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 tool has 9 optional parameters, no output schema, and no annotations, yet the description is a single sentence. There is no explanation of how to invoke the tool correctly, which parameters to use, or what the result of the check looks like. This is severely incomplete for a tool of this complexity and would leave an agent guessing at 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 coverage is 100%, so the baseline is 3, but the parameter descriptions are confusing and appear disconnected from the tool's purpose (e.g., 'City name for a public weather hint', 'JSON text to validate'). The description itself adds no explanation of how these parameters relate to checking a URL. It fails to compensate for the schema's lack of clarity, leaving the agent unable to determine which parameters are relevant or how to provide them.

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.' It distinguishes from siblings like normalize-url and fetch-status by focusing on openability, but it doesn't elaborate on what 'opened' means or how it differs from similar checks. The purpose is clear enough for a basic understanding, though it lacks nuance.

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 is given on when to use this tool versus its siblings. It doesn't mention alternatives or conditions that would make this tool preferable. The description only states what it does, leaving the agent to infer usage context, which is insufficient given the many URL-related sibling tools.

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