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

No annotations are provided, so the description must disclose behavioral traits. It states the tool checks reachability but does not explain how the check is performed (e.g., HTTP request, DNS lookup), what constitutes 'reachable', whether redirects are followed, or any timeouts. It also doesn't mention side effects or network requirements.

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 a single short sentence, 'Check URL reachability.' It is front-loaded with the verb and object, contains no filler words, and is appropriately sized for a tool with one parameter.

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?

There is no output schema, so the description should clarify what the tool returns (e.g., boolean, status code, error message). It also omits handling of invalid URLs, DNS failures, or timeouts, leaving the agent with insufficient information to interpret results.

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 0%, and the description does not explain the 'url' parameter beyond its name. It fails to specify URL format, allowed protocols, or examples, so it does not compensate for the schema gap.

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 the specific verb 'check' and the resource 'URL reachability', clearly distinguishing it from format validators like validate_domain and URL processors like url_normalize. While it is specific, it doesn't explicitly contrast with siblings such as monitor_url or read_url, so it earns a 4 rather than a 5.

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 provides no guidance on when to use this tool versus alternatives like monitor_url, redirect_trace, or ssl_check. There is no mention of use cases, prerequisites, or when not to use the tool.

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