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

Annotations already cover read-only, open-world, idempotent, non-destructive, and the description adds substantial context beyond them: the 200-URL cap, null handling for lastmod, the signed observation contents, the user agent used, that robots.txt may be read for a bare domain, the 1.5 MB per-file limit, and that nothing is stored. It also warns that sitemap addresses are data and are never fetched as instructions, which is meaningful behavioral disclosure.

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-loads purpose and input form, then output shape, then a compact limits block. Dense but nearly every clause carries information; the parenthetical listing the signed observation fields is the one spot that reads as run-on.

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?

No output schema exists, and the description compensates by explaining the return shape (URLs, lastmod, signed observation). For a one-parameter read tool with rich annotations, nothing an agent needs in order to call it correctly appears to be 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%, so the single parameter is already documented including the example.com form and the public http(s) sitemap address alternative. The description largely restates those input forms and adds only the implied robots.txt fallback for a bare domain, so the baseline of 3 applies.

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 resource and result: pages of a site with their lastmod dates, from a domain or sitemap address. It is clear what you get back (up to 200 URLs plus a signed observation). It does not explicitly differentiate itself from the nearest sibling (feed_read), which is the only thing keeping it from 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?

Gives clear context on acceptable input (bare domain or full sitemap address), scope limits (one level of index, max 5 children, 6 GETs), and exclusions (.gz sitemaps are not read, public http(s) on ports 80/443 only). It does not route the agent to alternatives when this tool is not the right pick.

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