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

Beyond the readOnly/idempotent/openWorld annotations, the description discloses cost ($0.002/call, x402 USDC on Base), expected latency (~2-5 s), what the output contains (0-100 score with issues and fixes), and a real operational constraint: it obeys robots.txt. The only gap is no note on what happens when robots.txt blocks the fetch or how failures are reported.

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?

Pricing and the core scope are front-loaded in the first two sentences, followed by the check list and a closing latency note. Dense but nearly every clause carries information; the bracketed "[SEO, security and site verdicts]" tag is the one piece of marginal filler.

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 an output schema present, the description does not need to explain return values, and it still covers cost, latency, compliance behavior and check coverage for a two-parameter read-only tool. An agent has everything required to invoke it, missing only explicit sibling routing.

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 both url and trial are already documented with examples and limits, and the baseline of 3 applies. The description reinforces the trial mechanism and adds the try_free alternative but contributes no format or syntax detail the schema lacks.

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 opens with a concrete verb+resource ("On-page SEO check of one URL") and then enumerates exactly what is inspected: title/meta lengths, H1, canonical, noindex, Open Graph, JSON-LD, alt text, compression, response time, plus robots.txt, sitemap, llms.txt and AI-crawler allowances. The "one page" scoping implicitly separates it from site-level siblings such as site_check, site_report and seo_audit_lite, though it never names an alternative explicitly.

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 is only implied by the enumerated check list and the "one URL" scope, so an agent can infer this is the single-page variant rather than the whole-site audit, but nothing states when to prefer it over seo_audit_lite, page_meta or security_scan_lite. The free-trial routing ("add trial: true or use try_free") is the only explicit when-to-do-X guidance.

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