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

Annotations already cover the safety profile (readOnlyHint, openWorldHint, destructiveHint), and the description adds meaningful traits beyond them: the data sources (robots.txt, sitemaps, homepage links), the 1,000-URL cap, per-URL lastmod/source, and — critically — the $0.0025 USDC per-call cost and x402 payment mechanics. Cost and payment path are behavior an agent must know before invoking, and none of it is in the annotations.

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 purpose, then alternatives, then params, then pricing — a sensible order with no wasted preamble. The payment sentence is dense but earns its place because cost is non-obvious; slightly compacted/truncated phrasing ('no pages to read') keeps it from a 5.

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 carries the return-value burden and does: URLs with lastmod and source, no page content. Combined with param ranges, cost, payment channel, and a runnable sample input, nothing an agent needs to call this correctly is missing.

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 50% (only url has a schema description). The description compensates by documenting both params inline — url accepts 'site or domain' (a semantic hint beyond the schema's terse text) and max_urls with its 1–1000 range and default 200. Most of this restates constraints already in the schema, so it adds value primarily for the undocumented max_urls, meriting a 4 rather than a 5.

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 and resource ('List the URLs of a website without reading them') and immediately bounds the scope. The contrast with reading tools (web-read-batch, site-crawl) lets an agent distinguish it from siblings without opening a schema.

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?

Explicitly frames itself as 'a cheap first step to decide which pages to read with web-read-batch or site-crawl', naming the downstream alternatives and the condition that selects them. Includes an affirmative note that it returns no page content, steering agents away from using it as a reader.

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