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

With no annotations provided, the description carries full burden and does substantial work: it discloses the lookup order (robots.txt then /sitemap.xml), how sitemap indexes are surfaced, and the per-call cost of $0.008 USDC. The cost disclosure is especially valuable behavioral context for an agent deciding whether to invoke. It stops short of describing failure behavior when no sitemap exists, a modest gap.

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?

Four sentences, each with distinct value: core function, usage guidance, edge-case index behavior, and cost. The most important information is front-loaded, and there is zero redundancy with the schema or title.

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 simple read-only enumeration tool with 2 parameters and no output schema, the description covers the essential ground: what is returned, how it is located, index handling, and pricing. The lack of an output schema raises some burden to describe return shape, which is partially addressed ('pages with last-modified dates'). Error and pagination details could round it out but are not critical.

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% for both parameters, so the baseline of 3 applies. The description adds implied meaning to the url parameter by explaining how the root URL is resolved (robots.txt first), but the limit parameter semantics are fully handled by the schema. The description does not need to compensate for any schema gap.

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?

The description states the specific resource ('pages a site declares in its sitemap'), the data included (last-modified dates), and the discovery method (robots.txt first, /sitemap.xml second). This clearly differentiates it from sibling tools like resolve_url and url_headers, which handle URL mechanics rather than content enumeration.

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?

Explicit use cases are given: enumerate a documentation set or blog archive before deciding what to read. The phrase 'instead of crawling blindly' provides an exclusion condition. The sitemap-index note ('call again for the child sitemaps') advises a follow-up action. It doesn't name sibling alternatives, but the siblings serve clearly different purposes, so the omission is minor.

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