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

Annotations already mark the tool read-only and non-destructive, so the description does not need to re-state safety. It adds the behavioral fact 'No browser is launched', which is not captured by the annotations and is material to how the check is performed. It does not detail network behavior, but the annotations lower the bar.

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, with the key scope statement first and the crucial behavioral caveat second. Every word 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?

Despite having seven parameters and no output schema, the description only gives a one-line purpose. It leaves unclear what 'can be opened' measures (status? reachability?), what the return value is, and how the non-URL parameters are meant to be used, so an agent is not fully equipped to invoke it confidently.

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 description coverage is low: seven parameters exist, and the tool description only references 'a URL' without explaining how ref, city, feed, host, json, or path relate to the check. The schema provides some per-parameter text, but the description adds almost no meaning and does not compensate for the low 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 uses a specific verb 'Check' with resource 'URL' and an outcome ('can be opened'), and the second sentence 'No browser is launched' distinguishes it from browser-based siblings like playwright-url-ok. This makes the tool's purpose immediately identifiable and differentiable.

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 statement 'No browser is launched' implies this is the lightweight alternative to browser-based tools, but it never explicitly says when to choose this tool over siblings or names exclusions. The usage context is implied rather than stated.

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