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

Annotations cover read-only/open-world, and the description adds substantive non-obvious behavior: analysis is from raw HTML only, results are pass/fail per check, and there is a per-call price paid via x402 on specified chains with failed calls not charged. Cost and payment mechanics are exactly the kind of context an agent needs before invoking.

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?

Purpose is front-loaded in the opening clause and the enumerated checks are compact and informative. The closing pricing/payment sentence is long and slightly buries the cost detail, but it is non-redundant 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?

An output schema exists, so return values need not be fully specified, yet the description still sketches the result shape (each check with value and pass/fail). With annotations covering safety, scope and pricing covered, nothing an agent needs to call this correctly is missing.

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% on the single 'url' parameter, so the schema already carries the definition ('Full http or https address'). The description only reinforces that it must be a public page, which is marginal added meaning beyond the structured field.

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 ('On-page SEO audit of one public page from its HTML only') and enumerates the exact checks performed, so the agent knows precisely what the tool reports. It also bounds scope by naming exclusions (Core Web Vitals, backlinks, keyword volumes), which separates it from broader SEO or crawler siblings.

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?

Usage context is clear: one public page, HTML-only analysis, no rendering-dependent metrics. The negatives ('No Core Web Vitals, backlinks or keyword volumes') tell the agent when not to expect results, but no sibling alternative is named for those cases, so it falls short of explicit routing.

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