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

Annotations already indicate readOnly, openWorld, idempotent, and non-destructive. The description adds behavioral context: no JavaScript execution, no access control bypass, caching behavior via 'fresh' parameter, and that it returns the final URL. This adds value beyond annotations.

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 three sentences, front-loaded with purpose. Every sentence is informative without redundancy. No filler or unnecessary words.

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 description covers key behavioral aspects (caching, restrictions) and the output schema exists, so return values are documented elsewhere. Missing details like error handling or rate limits, but the tool is simple enough that it's adequate.

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 coverage is 100%, so the schema already documents both parameters. The description largely repeats schema info (e.g., url must be public, fresh caching). It adds little new meaning beyond what the schema provides.

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 specific verbs ('Check') and clearly identifies the resource ('HTTP reachability, status and final URL'). It distinguishes from sibling tools like web.url.text or web.url.content_type by focusing on basic reachability and status, not detailed content extraction.

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 explicit usage constraints ('Use only for public HTTP(S) resources; it does not execute JavaScript or bypass access controls') and guidance on the 'fresh' parameter. However, it does not explicitly name alternative sibling tools for different use cases.

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