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

No annotations are provided, so the description must carry the full burden. It discloses only that no browser is launched, but fails to describe what the tool actually does (e.g., performs a HEAD request, validates URL format, checks DNS). The parameter list includes unrelated fields (city, json, path, zone, query) with no explanation, making behavior ambiguous.

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 sentences with no waste; the key constraint (no browser) is front-loaded. However, it is so sparse that it borders on under-specification, so a 4 rather than 5.

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 tool with nine optional parameters and no output schema, the description is inadequate. It doesn't explain what the tool does with the parameters (e.g., 'ref', 'city', 'feed', 'json', 'path', 'zone', 'query' are unrelated to URL checking), nor what it returns. An agent would be left guessing about the tool's actual behavior and output.

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 100%, so the schema already documents each parameter. The description adds no additional semantics about how these parameters interact with the URL check, but the baseline of 3 applies since the schema covers the parameters.

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 clear verb-resource pair: 'Check whether a URL can be opened' with the clarifying caveat 'No browser is launched.' This distinguishes it from 'playwright-url-ok' which likely launches a browser. However, it doesn't specify the method (HTTP request, DNS, etc.), so it's 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?

Provides no guidance on when to use this tool versus siblings like 'fetch-status', 'normalize-url', or 'playwright-url-ok'. No alternatives or exclusions are mentioned, leaving the agent to infer from the name alone.

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