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

Annotations already declare readOnlyHint, openWorldHint and idempotentHint, so the safety profile is covered. The description adds useful context: it operates on *public* URLs (implying a live network fetch and no auth), and it discloses the two specific checks performed rather than just saying 'check'. No rate-limit or failure-mode detail is given.

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 tight sentences that front-load the operation and immediately follow with the usage condition. Every clause earns its place with no padding.

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 an output schema present, return-value detail is unnecessary, and the description still names the two reported facts. Combined with annotations covering the safety profile, an agent has enough to call it correctly; only edge-case behavior (e.g., missing/404 robots.txt) is unaddressed.

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% and the single url parameter is fully documented, including the page-URL-to-/robots.txt resolution behavior. The description's URL guidance largely restates the schema, so it adds little beyond the baseline.

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 (fetch) and resource (public robots.txt) and specifies exactly what it reports: whether the wildcard group blocks the site and whether Sitemap lines are absolute. This is more precise than most siblings, though it does not explicitly contrast itself with adjacent tools like validate_sitemap or check_http_headers.

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 a clear when-to-use condition ('when you have a URL') and a when-not exclusion ('not a pasted file'), which steers input format correctly. It stops short of naming an alternative sibling tool, so it isn't a full 5.

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