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

With no annotations, the description carries the full disclosure burden. It only reveals that no browser is launched, omitting whether a network request is made, what exactly is checked, and how the many other parameters are handled. The schema's 'discarded after the shape check' language hints at a different behavior than 'can be opened,' adding confusion.

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 and front-loaded, with the key behavioral distinction ('No browser is launched') placed immediately after the purpose. It earns its place without repetition, though it is terse enough to sacrifice important 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?

For a tool with no annotations, a large parameter set, and no output schema, this description is incomplete. An agent cannot determine the return value, required inputs, or the precise semantics of an 'ok' result. It also fails to distinguish itself from the many sibling URL/network tools beyond the 'no browser' note.

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 input schema already provides descriptions for all parameters, so schema coverage is high. The description adds little beyond singling out the URL, and it does not clarify which of the many parameters are relevant or required, nor that most are discarded. This is consistent with the baseline 3 for high schema coverage.

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') and resource ('URL'), and the second sentence explicitly differentiates it from browser-based alternatives by noting 'No browser is launched.' However, 'can be opened' is ambiguous—it could mean shape validation, network reachability, or rendering—so the purpose is clear but not fully precise.

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 explicit guidance on when to use this tool versus alternatives. The 'No browser is launched' clause is a negative constraint but does not tell the agent when to prefer this over siblings like browser-url-ok, fetch-status, or web-fetch. Usage context must be inferred.

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