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

Annotations already cover read-only, idempotent, non-destructive and open-world, so the bar is lower, and the description still adds real context: the check runs from Cloudflare's network (a specific vantage point), performs DNS resolution before a single HTTP request, and reports distinct failure classes rather than a bare boolean. It omits timeouts, caching, and redirect-following behavior, keeping it from 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?

Two compact sentences, front-loaded with the core action and the vantage point, followed by the result taxonomy. No filler, and the phrase 'DNS first, then one request' efficiently conveys the probe sequence.

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 single-parameter read-only check with full schema coverage and rich annotations, this covers what an agent needs to call it and interpret results, including the three distinguishable outcomes. It lacks any indication of latency/timeout expectations or what the response payload looks like, which matters since no output schema exists.

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?

One parameter with 100% schema description coverage, so the schema already explains the accepted URL forms and the public-site/standard-port restriction. The description adds only the implicit 'from Cloudflare's network' framing, which does not extend the parameter's meaning beyond the schema.

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 specific verb and resource ('Checks whether a website is reachable') plus the vantage point ('from Cloudflare's network'), and enumerates the three outcomes it separates. It does not differentiate from the closely overlapping sibling url_status_check, so it stops short of 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?

There is no when-to-use or when-not guidance, and no routing to alternatives such as url_status_check, http_headers_check, or dig despite heavy sibling overlap. The three-outcome framing hints at diagnostic use, but the agent must infer selection on its own.

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