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

No annotations are provided, so the description carries the full burden. It discloses that no browser is launched, but it does not explain what actually happens to the many parameters (e.g., are they all validated? Why does a URL check accept a timezone?). The description is inconsistent with the parameter set, implying behavior that is not true to the tool's actual function.

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 short (one sentence), but it is under-specified. It lacks essential details about the tool's real purpose and behavior. This is not appropriate conciseness but rather omission of critical information.

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?

With nine parameters, no annotations, and no output schema, the description is completely inadequate. It does not explain what the tool checks, what outputs are produced, or how the parameters interact. The agent cannot reliably invoke this tool based on the provided information.

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?

While the schema provides 100% coverage with individual parameter descriptions, the tool description does not add meaning beyond that. More importantly, the description's narrow focus on URLs contradicts the broad parameter set, leaving the agent confused about why city, json, and zone parameters exist. The schema descriptions are clear, but the tool-level description fails to unify 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 says 'Check whether a URL can be opened,' which is a clear verb and resource, but the input schema includes nine unrelated parameters (city, json, zone, query, etc.) that are not about opening a URL. The description does not reflect the tool's actual scope, making it misleading and not distinguishing it from siblings like normalize-url or fetch-status.

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 on when to use this tool versus alternatives. The description only states what it does (or claims to do) without any exclusions or contextual cues. Given the sibling list includes many specialized validators, the agent has no way to choose this over others.

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