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

With no annotations, the description carries the burden and does reasonably well: it discloses sitemap-index recursion, robots.txt fallback discovery, that results carry last-modified dates, and a concrete price of 0.002 USDC per call via x402. It omits failure behavior (no sitemap found), truncation semantics, and any rate/latency expectations.

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?

Two sentences, zero filler, front-loaded with the fetch/index/follow behavior and closed with the pricing fact an agent needs before calling. Every clause earns its place.

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, so the description rightly states what comes back (URLs plus last-modified dates) and pre-empts the confusing part of the payment handshake by naming x402 pricing alongside the schema's proof flow. Missing only edge-case behavior (empty/absent sitemap, malformed XML) for full completeness.

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 67% and the two descriptive schema fields (url, paymentProof) already explain their roles, so the baseline is 3. The one genuinely undocumented parameter, limit (default 200, max 1000), is never mentioned in the description, so the description adds nothing about how result count is capped.

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+resource chain: fetches sitemap.xml (or the one from robots.txt), follows sitemap indexes, returns URLs with last-modified dates. That is far more concrete than a generic fetch. It does not explicitly draw the boundary against the closest sibling, robots_check, which also reads robots.txt, so an agent must infer the split.

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?

Usage is only implied by the mechanics of the description — you'd use it to enumerate a site's pages. There is no explicit 'use this when you need X, use web_extract/link_extract/robots_check instead' guidance, and no mention of prerequisites (e.g. the site must actually publish a sitemap).

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