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

With no annotations, the description carries the full burden and does well: it discloses that the call is keyless (no auth), free, capped at 20 URLs, and sourced from robots.txt with a /sitemap.xml fallback, plus the lastmod payload. It doesn't cover failure behavior for invalid/unreachable domains or any rate limiting, which are the remaining gaps.

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, both dense with decision-relevant facts, and the free-tier capability and limits are front-loaded before the paid alternative. No filler.

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?

Absent an output schema, the description compensates by stating the return shape (up to 20 URLs with lastmod) and the sitemap discovery sources, which is what an agent needs to call it correctly. Error/empty-result behavior is the only unaddressed piece.

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%, and the 'site' description already covers the domain/URL/direct-.xml forms; the description adds no syntax or format guidance beyond that. 'contains' is only referenced in the context of the paid tool, so the free tool's own filter semantics get no extra explanation. 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 specific verb and resource ('discover a domain's sitemaps', 'return up to 20 page URLs with lastmod') and explicitly positions itself against the paid /web/sitemap alternative. An agent can distinguish it from get_premium_access without opening either 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 the free/keyless option versus the paid '/web/sitemap ($0.003)' that returns 5000 URLs across 10 files, and routes the agent to 'get_premium_access' when the larger result or substring filtering is needed. The selection condition between the two is spelled out rather than inferred.

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