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

Goes well past the annotations by disclosing the paid model ($0.05/call via x402, USDC on Base), the exact retry protocol (first call returns payment terms; pay and retry with _meta["x402/payment"]), and expected latency (~3-8 s). These are operational facts an agent cannot get from readOnlyHint/idempotentHint/openWorldHint and would otherwise fail on.

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?

A tight four-sentence block with no filler; each clause carries either scope, use case, or payment mechanics. The payment sentence is dense but load-bearing, though leading with price ahead of what the tool does slightly buries the purpose.

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 composite read-only tool with no output schema, the description covers the four result families, the price/payment flow, and runtime — enough for an agent to call it and handle the 402-style handshake. It stops short of describing failure modes (unreachable sites, non-public URLs) or the result shape, which is acceptable given the annotation coverage.

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 the single parameter is already fully documented (public http(s) URL or bare domain). The description only adds 'for a website', which does not extend meaning beyond the schema — the baseline 3 for high-coverage schemas 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 resource (a website) and enumerates exactly what is returned: on-page SEO score/issues, security headers/TLS grade, tech stack, and SPF/DKIM/DMARC. That enumeration cleanly separates it from the single-purpose siblings (seo_page, security_headers, tech_stack, email_auth) and from the verdict-style site_verdict.

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 concrete use cases (lead qualification, vendor due diligence) and a clear positioning rule: 'a first look before a full audit', which implies the deeper audit tools come later. It does not name a specific alternative or state exclusions, so it falls short of a 5.

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