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

With no annotations, the description carries the full burden. It discloses that no browser is launched, but does not explain what 'can be opened' means (e.g., HTTP status, network request), possible side effects, rate limits, or the return value.

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?

A single, front-loaded sentence efficiently communicates the core purpose and a key behavioral trait. It is appropriately concise for a simple check tool, though it lacks structured detail.

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 tool has no annotations or output schema, and the description covers only the basic premise. Given the broad input schema with multiple unrelated-looking fields, the description is insufficient for an agent to fully understand how to invoke the tool correctly (e.g., which input to provide, expected output format).

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 has 100% coverage with descriptions for every parameter, so the baseline is 3. The description adds no parameter-specific context beyond what's in the schema, and it does not clarify which parameter is the primary URL to check among the many optional-looking fields.

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 clearly states a specific action ('Check whether a URL can be opened') on the URL resource. The key differentiator 'No browser is launched' helps distinguish this from the sibling browser-url-ok, even without naming it.

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 implicitly suggests a lightweight check by noting no browser is launched, which implies it might be preferred over browser-url-ok for faster checks. However, it does not explicitly state when to use this tool versus alternatives or mention any exclusions.

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