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

With readOnly/idempotent/openWorld annotations already covering the safety profile, the description adds real operational context: hard limits of 8 s, 5 redirects, 768 KiB, and 50 sitemap declarations, plus the caveat that the answer is guidance rather than authorization. It stops short of stating behavior for the common edge cases — robots.txt missing (404), unreachable, or non-200 — which materially affects how an agent should interpret the result.

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?

Three dense sentences, front-loaded with the core action and evaluation rule, then usage guidance, then limits. No filler; every clause carries information an agent needs.

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?

An output schema exists, so return values needn't be spelled out, yet the description still names them (crawl delay, sitemaps) and enumerates fetch limits. The remaining gap is failure/absence semantics for robots.txt and how the result should be represented when no policy is found — relevant for a three-required-parameter tool with mostly undocumented parameters.

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 only 33% (only 'url' is documented), so the description has to compensate and largely does: 'one path for a named user agent using longest-match allow/disallow precedence' explains what path and user_agent actually mean for the evaluation. It does not clarify wildcard handling for user_agent ('*' default) or that path defaults to root, leaving a small gap against the low coverage.

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 ('fetches an origin's robots.txt') plus the exact evaluation semantics (longest-match allow/disallow precedence for one path and user agent), and adds secondary outputs (crawl delay, sitemaps). This clearly separates it from siblings like inspect_url and parse_sitemap, which fetch or parse but do not evaluate robots policy.

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?

'Use this before automated retrieval' gives a clear triggering condition, and 'the result is policy guidance, not authorization' sets expectations about how to act on the output. It does not name alternatives (e.g., inspect_url for general header/status inspection), so the when-to-use side is strong while the when-not/alternative side is absent.

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