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

Goes beyond the annotations by disclosing that both HTTPS and HTTP are tested, that the response includes timing and redirect detection, the exact return shape, and that no login is required — useful auth context not in the structured fields. It doesn't mention timeout behavior or what happens for non-resolving domains, so not a 5.

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?

Four tight sentences, front-loaded with what is tested, followed by the return shape and then the trigger scenarios. Every sentence carries information an agent would otherwise have to infer.

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?

With no output schema, the description compensates by enumerating the returned fields, and it also covers the input meaning, usage triggers, and auth requirement. For a one-parameter read-only probe, nothing essential to correct invocation is missing.

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% and the single 'domain' parameter already carries an example format, so the schema does the heavy lifting. The description adds no constraint (e.g., scheme-less vs. full URL handling) beyond what the schema states — 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?

Specific verb+resource: 'Check whether a website is up and reachable right now,' with the probe scope (HTTPS and HTTP, status code, response time, redirects) spelled out. It is implicitly distinguishable from neighbors like check_ssl or trace_redirects, but never names a sibling to draw that boundary explicitly.

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?

Gives concrete trigger phrasing — 'is my site down?', 'why is my website not loading?', 'any question about site availability' — so the agent knows when to reach for it. It offers no when-not guidance or named alternative (e.g., when to prefer diagnose_my_server or get_my_site_health instead).

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