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

Annotations cover the safety profile (readOnly, idempotent, non-destructive, openWorld), and the description adds substantial behavior beyond them: robots.txt Sitemap directive precedence, fallback chain to /sitemap.xml then /sitemap_index.xml, one level of index nesting, gzip handling, the default 150,000 cap, an always-reported truncation notice, and found:false rather than an error when no sitemap exists.

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?

Front-loaded with the core action and its scope before any elaboration, then walks through fallback behavior, capping, and edge cases in dense, non-redundant clauses. The content-farm rationale earns its length by justifying the tool's purpose, and nothing repeats structured fields.

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?

Despite no output schema, the description conveys the return shape ('URL counts by path prefix'), the truncation signal, and the found:false no-sitemap case, plus the full discovery/fallback procedure. Everything an agent needs to call it and interpret the result is present.

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 both params (domain, max_urls) are already fully documented in the schema, including the default and hard ceiling. The description's mention of the 150,000 cap reinforces but does not extend the schema, so the baseline 3 is correct.

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?

Names a specific verb (fetch, report) and resource (a domain's sitemap structure), and sharply delimits scope: 'URL counts by path prefix — not their content.' No sibling tool covers sitemaps, so the purpose is unambiguous even without a named alternative.

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 concrete motivating context ('the fingerprint that separates a normal site from a programmatic content farm') and a worked example, which tells the agent when this tool is the right choice. It stops short of naming an alternative or an explicit when-not-to-use condition, so it doesn't reach 5.

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