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

Annotations are absent, so the description carries the burden. It discloses one behavior—no browser launch—but not whether a network request occurs, whether it only validates URL shape, or what it returns.

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?

Two short sentences, no filler, and the purpose is front-loaded. The behavioral note earns its place.

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 schema with nine optional params and no output schema, the description is not complete enough: it omits return semantics, side effects, and the role of the many parameters.

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 description adds no parameter-level guidance, and the schema's parameter descriptions (e.g., 'normalize or cite', 'weather hint', 'length check') do not clearly relate to checking whether a URL can be opened. With nine optional parameters and no required URL, the description should clarify which parameter to supply.

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?

States a concrete action ('Check whether a URL can be opened') and the resource ('URL'). The added note 'No browser is launched' distinguishes the check from browser-based alternatives, though the criteria for 'can be opened' are not specified.

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 prefer this tool over siblings like browser-url-ok, web-fetch, or normalize-url. 'No browser is launched' hints at a lightweight check but does not state the circumstances or alternatives.

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