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

Annotations already declare readOnly, idempotent, openWorld, and non-destructive, so the safety profile is covered. The description adds genuinely new behavioral context: it is billed at $0.005 USDC per *successful* call via x402 on Solana, and the returned allow/disallow entries are explicitly *samples* rather than complete lists — an important expectation to set. It does not disclose rate limits, caching, or failure/billing-on-error behavior, which keeps it at 4.

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 action and the return shape in one dense sentence, then use cases, then pricing and the HTTPS alternative. Every clause carries information, though the duplicated HTTPS endpoint invitation is somewhat promotional and adds length without changing how the tool is called.

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 correctly takes on the job of describing return values and does so concretely (sitemap index vs urlset, URL counts, sample locs). Pricing and the alternate endpoint are also covered. Minor gaps remain around crawl depth/timeouts and what happens when a domain has no robots.txt or sitemap.

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?

There is a single parameter with 100% schema description coverage, so the schema already documents it and the baseline of 3 applies. The description reiterates that the input is a domain ("for a domain") but does not clarify whether a bare hostname, a full URL, or a subdomain is accepted, which is the one ambiguity an agent would want resolved.

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 names a specific verb pair (fetch and parse) and precise resources (robots.txt plus discovered sitemaps for a domain), then enumerates the exact data points returned (user-agents, allow/disallow samples, sitemap index vs urlset, URL counts, sample locs). An agent knows exactly what this does. It stops short of 5 because it never contrasts itself with plausibly overlapping siblings such as seo_audit, headers_audit, or http_probe.

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?

"Useful for crawl planning and AI agent politeness checks" gives usage context, but it is a general motivation rather than a when-to-use rule. There are no exclusions, no prerequisites, and no pointer to which sibling to pick when crawl-related data is needed instead.

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