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

Annotations declare readOnlyHint and openWorldHint, so safety is already covered; the description adds genuinely non-structured behavior — x402 payment requirement, no charge when the page can't be fetched, and the 0-100 score plus severity-listed issues. Missing only things like rate limits or timeout behavior.

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?

Front-loaded with the purpose, then the check list, then cost and output notes — logical ordering. The long enumeration is dense but each item conveys a distinct capability, so little is wasted.

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 still tells the agent what comes back (0-100 score and issues by severity), plus the billing model and the fetch-failure exception. For a single-parameter read-only audit tool, nothing essential 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?

Only one parameter and schema description coverage is 100%, so the schema already explains 'url' as an absolute HTTP/HTTPS page URL. The description adds no format, normalization, or edge-case guidance beyond that, so 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?

Names a specific verb and resource ('SEO check for one page') and then enumerates the exact signals inspected (meta robots, X-Robots-Tag, robots.txt, title/meta description length, canonical, H1, viewport, language, OG tags, sitemap, HTTPS, redirects). An agent can distinguish it from check_site_safety or domain_report on scope alone.

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?

Gives clear usage context ('useful for site audits and pre-launch checks') and points to list_prices for the paid flow, but never explicitly states when to pick check_site_safety or domain_report instead for overlapping site concerns. Clear context, no exclusions.

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