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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the agent knows this is a safe read operation. The description adds valuable behavioral context: it fetches a live page, defaults to the home page, and reports DNS-to-hosting status. It does not contradict annotations. It could mention network variability or that the page must be publicly reachable, but the existing disclosure is solid.

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, well-structured sentence that front-loads the core action and then lists the reported outputs. Every clause earns its place, and there is no redundant repetition of the title or schema.

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?

Given the output schema exists, the description need not explain return values. The description covers the tool's purpose, default behavior, and key outputs. It could be slightly more explicit about when to prefer this over get_site_info, but overall it is complete enough for an agent to select and invoke it correctly.

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 both parameters. The description adds meaning by explaining that 'path' defaults to the home page and that 'site' is the domain as shown by list_sites, which helps the agent understand the relationship between the two parameters. This exceeds the baseline 3.

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 states a specific verb ('Fetches') and resource ('a page from the live website'), and enumerates exactly what is reported: HTTP status, SSL, page title, text preview, and DNS pointing. This clearly distinguishes it from siblings like get_site_info or list_sites, which are about site metadata rather than live page fetching.

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 implies when to use it: when you need to inspect a live page's HTTP status, SSL, title, preview, or DNS-to-hosting mapping. It does not explicitly name alternatives or exclusions, but the context signals and sibling list make the use case clear. A 4 is appropriate because it gives clear context without explicit when-not-to-use guidance.

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