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

With no annotations, the description carries the full burden of disclosing behavior. It states only that 'No browser is launched,' which is a useful negative constraint, but it does not explain how the check is performed (e.g., network request, DNS lookup, syntax validation), what constitutes 'can be opened,' or what the return value looks like. This is a significant gap for a tool with no other behavioral metadata.

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 exceptionally concise at two short sentences with no filler. It front-loads the core purpose first, then adds a key behavioral caveat. This is efficient and well-structured, though it sacrifices depth for brevity. The conciseness is appropriate, but the structure does not earn the top score because it omits crucial context.

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 severely incomplete given the tool's complexity. It has 9 optional parameters with no required ones, and the description does not explain how they relate to the core function (e.g., why 'city' or 'json' matter). There is no output schema, and the description gives no indication of what the tool returns or how results are expressed. An agent cannot reliably decide when to call this tool or how to interpret its output based solely on this description.

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% with each of the 9 parameters having a description, so the baseline is 3. The tool description adds no additional parameter context or relationships beyond the schema. Since the schema is detailed, the tool's lack of parameter explanation does not lower the score, but the description also does not enrich the semantics beyond what the schema already provides.

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 ('check whether a URL can be opened') and a specific resource (URL). It also adds a distinguishing trait ('No browser is launched') which implicitly differentiates it from siblings like browser-url-ok, but it does not explicitly name any alternative. The purpose is clear and specific enough for an agent to understand the core function, though sibling differentiation is only implicit.

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 the many siblings (browser-url-ok, fetch-status, normalize-url, etc.). It does not mention contexts where it would be preferred, nor does it indicate any prerequisites, limitations, or alternatives. An agent has to infer usage from the name and description alone, which is insufficient.

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