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

Beyond the annotations (readOnly, idempotent, openWorld, non-destructive), the description discloses concrete operational traits: an implicit robots.txt network fetch, the shape of the result (counts, lastmod range, samples, protocol issues), and a hard rate limit of 10 free calls/day with two payment paths. That rate-limit and payment context is exactly the kind of behavior annotations cannot express. It stops short of saying what happens when no sitemap is found or when robots.txt blocks access.

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?

Purpose is front-loaded in the first clause, with outputs, then commercial terms appended. Every sentence carries information, though the x402 payment-parenthetical is dense vendor boilerplate that could be trimmed without losing decision-relevant meaning.

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?

An output schema exists, so the description need not document return values, yet it still summarizes them helpfully. Combined with cost/rate-limit disclosure, an agent has enough to decide and invoke; only failure modes and whether a site URL versus direct sitemap URL behaves differently are left unstated.

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% and both parameters are already documented as "site or sitemap URL" and "sample size". The description's mention of finding the sitemap via robots.txt and returning "sample URLs" loosely corroborates the `url` and `limit` semantics, but adds no format, default, or boundary detail beyond the schema.

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 compound verb ("Find ... and parse") and a precise resource ("a sitemap or sitemap index"), then enumerates what it extracts (URL count, lastmod range, sample URLs, protocol issues). It is clearly distinguishable from siblings like feed_parse or broken_links by resource, but it never names an alternative to route against.

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 implied rather than stated: the "via robots.txt" phrasing tells the agent the tool will auto-discover a sitemap from a site URL, which is a useful when-to-use signal. There is no explicit when-not-to-use guidance and no named alternative for cases like parsing an already-fetched XML document.

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