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

Goes well beyond the readOnlyHint/openWorldHint annotations: it discloses determinism (no AI), the discovery fallback chain (robots.txt, else /sitemap.xml), the exact validation checks performed, and the auth/cost model (x402 USDC payment on Base, first 5 calls/day free). That pricing and rate-limit detail is genuinely useful pre-invocation context.

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 discovery logic, then validation specifics, return format, and cost in descending priority. Every clause carries information, though the validation list is dense enough to read as a 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?

With no output schema, the description compensates by stating what is returned (sample URLs or child sitemaps) plus the validation semantics and payment/auth requirements. An agent has everything needed to call it correctly and interpret the result.

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's dual meaning (site URL vs sitemap URL) is already stated verbatim in the schema. The description restates the same dual mode without adding syntax, format, or edge-case detail beyond it, so baseline 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 specific verbs and resource: finds a site's sitemap or validates a given sitemap URL, and enumerates exactly what is validated (urlset vs sitemapindex, entry count, lastmod, gzip). This clearly distinguishes it from robots_check (which parses robots.txt) even though only the discovery fallback references robots.txt.

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 for both invocation modes: pass a site URL to discover the sitemap, or pass a sitemap URL to check it directly. However, it never names robots_check or ai_crawler_access as alternatives or states when this tool is the wrong choice, so it stops short of explicit routing guidance.

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