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

Annotations already cover the safety profile (readOnlyHint=true, openWorldHint=true), and the description adds genuinely new behavior: the discovery strategy with fallback ('robots.txt, else /sitemap.xml'), the same-site restriction, the hard cap (<= 5,000), and the cost ('Costs 1 credit'). It does not describe behavior when no sitemap exists or any rate-limit/throttling considerations.

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?

A single dense sentence with the purpose and source method front-loaded, followed by the routing hint and cost. No filler, no repetition, every clause carries information the agent needs before calling.

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 still conveys what comes back (a capped list of same-site URLs) and how it is derived. Combined with full schema coverage and clear annotations, an agent has everything needed to invoke it correctly.

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%, so all four parameters including the include_paths/exclude_paths regexes are already documented in the schema. The description only restates the limit cap (<= 5,000) that the schema already declares, adding no new meaning. 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 a precise verb+resource ('List a website's URLs') and immediately scopes it with 'without fetching its pages', which cleanly separates it from contextfetch_extract_url and contextfetch_crawl. It also discloses where the URLs come from (sitemaps, start-page links, same site only), so an agent understands the result set without opening the 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 routes the agent: 'Use it to find the right pages before contextfetch_extract_url or contextfetch_crawl', naming two concrete alternatives and the ordering relationship. It lacks an explicit when-not condition (e.g., a single known URL should go straight to extract_url), so it falls just short of the top bar.

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