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

Very rich beyond the annotations: it discloses caching behaviour and cached_at, that another host's URLs are counted but never requested, that a sitemap index expands to at most 5 sitemaps, that a new sample consumes one audit from the daily allowance, and that exhaustion yields 402 with accepts[] mirroring POST /api/audit. These are exactly the quota/side-effect details an agent needs, and they are consistent with readOnlyHint=false and idempotentHint=false rather than contradicting them.

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?

The text is heavily redundant: 'URLs of another host are counted, never requested' appears twice verbatim, and the one-hour cached-sample rule is stated twice. The front-loaded opening summary is good, but the middle section re-lists checks already named in the first sentence, inflating length without adding information.

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?

For a no-output-schema tool it does enumerate the findings the response will contain (non-200s, redirects, robots blocks, noindex, canonicals, title/description problems, price mismatches) and the allowance/error behaviour. It is missing only the shape of the result object and how many findings per URL are returned, which are the remaining gaps an agent would want.

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 the baseline is 3. The description adds a little that the schema does not make obvious — that any address of the site is acceptable and that no account is needed, which implicitly explains guest_token — but it adds no detail on lang or guest_token formats.

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 and resource — it reads /sitemap.xml, checks the first 20 URLs of the same host, and reports on status, redirects, robots.txt, noindex, canonical, titles/descriptions and price mismatches. It calls itself 'the free sample of the SEO audit', which gives a rough scope boundary, but it never explicitly distinguishes itself from the sibling audit_url or get_audit.

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?

It states cost and prerequisites ('Free, without an account') and the caching condition (same site within one hour returns the stored sample), which helps an agent decide whether to call it. However there is no explicit when-to-use-this vs use-audit_url/get_audit-for-that guidance, so routing among the many audit siblings is left to inference.

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