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

Annotations already declare readOnly, idempotent, openWorld, and non-destructive, so the safety profile is covered. The description goes beyond them with real behavioral context the annotations cannot express: a hard cost ($0.20 USDC), two payment mechanisms with required headers, and exclusion from the free trial — the main reason a call would fail.

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?

One dense but front-loaded sentence leads with the capability and its measurable outputs, then a second sentence covers payment and access. Every clause carries information (checks, page cap, score) though the payment sentence is packed tightly enough to require a second read.

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 burden of telling the agent what comes back — the specific check list, robots/sitemap coverage, brand ranking, and a 0-100 score — which it does. Auth and cost are covered; the only gap is no guidance on alternatives or expected latency for a multi-page audit.

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 100%, so every parameter is already documented and the baseline is 3. The description reinforces semantics by tying 'pages' to a maximum of 8 audited top pages and 'brand' to brand-query ranking, but it adds nothing for 'gl' (country code) and doesn't explain defaults beyond what the schema 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?

The description names a specific verb+resource (SEO audit of a domain) and enumerates the concrete outputs: search-indexed pages, title/meta/h1/canonical/noindex/alt checks on up to 8 pages, robots.txt and sitemap, brand-query ranking, and a 0-100 score. That level of detail lets an agent distinguish it from crawl_site (raw crawling) or ai_visibility_check 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?

It supplies critical usage prerequisites — x402 payment of $0.20 USDC on Base or Solana via X-PAYMENT, or a prepaid Bearer xs_ key, plus the fact it is excluded from the free trial. However, it never states when to prefer this over sibling tools such as crawl_site, competitor_report, or ai_visibility_check, so routing guidance is only implied by the output list.

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