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

Annotations only declare readOnlyHint and openWorldHint; the description adds genuinely decision-critical behavior: a concrete price ($1.5 USDC via x402), a non-charge condition when too few sources respond, and the async nuance that the core source is validated before a job is queued and charged. That is exactly the kind of cost/refund/timing context an agent cannot infer from 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?

A single dense sentence, but it is front-loaded with the purpose and then layers on cost and async caveats. Every clause carries information; slightly long but not padded.

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 carries the return-value burden and does so: prioritised fixes with how-to, per-page scores, and a PDF. It covers cost, async, and refund edge cases. Minor gap is that webhook_url is never mentioned in the prose, leaving that parameter to the schema alone.

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 80%, so the baseline is 3. The description reinforces scope ("up to 10 pages", PDF output) and clarifies async charging semantics, but adds no format or syntax detail for domain, pages, or webhook_url beyond what the schema already states.

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?

Opens with a specific verb+resource ("Multi-page SEO audit") and enumerates the exact checks performed (titles, meta, headings, canonical, indexability, structured data, images, links, headers). This is clearly distinguishable from siblings like seo, sitemap, crawl, or domain_audit, which do narrower single-purpose jobs.

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?

Explains the billing and async mechanics, which implicitly tells the agent when to use async=true, but never says when to prefer this over sibling tools such as report_domain or domain_audit, nor any prerequisites beyond a domain. Usage is implied rather than routed.

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