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

Far beyond the annotations: it discloses the return shape (0-100 score, safe/caution/dangerous verdict, per-signal explanations), the heuristic/no-blocklist limitation, the paid model (0.005 USDC via x402 on Base or Solana, no account/API key), the failure semantics (invalid input refused before payment, failed runs never charged), and the unpaid path (x402 PaymentRequired). That is exactly the operational context annotations cannot carry for a paid, open-world tool.

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 decision question, then the checks, then the result contract, then payment logistics — a logical order. It is dense but long; the pricing/refund sentences are necessary for a paid tool, though the trailing 'same tool over HTTP' URL and sample-answer pointer add bulk beyond core selection value.

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?

No output schema exists, and the description fully compensates by describing the return values (score, verdict, explained signals). Combined with the payment and error-path disclosure, an agent has everything needed to decide whether to call it and to interpret the response.

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?

There is a single required parameter with 100% schema description coverage, which sets the baseline at 3. The description adds an example URL and an equivalent HTTP calling form, but nothing new about the parameter's semantics (e.g. whether bare domains without scheme are accepted, or how redirects affect the input).

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 ('checks the final site' behind a link) and enumerates exactly which signals are inspected (RDAP domain age, TLS, punycode, brand impersonation, drainer patterns), which separates it cleanly from siblings like site_audit, link_preview and domain_intel. The framing question 'Should an agent open, sign or pay this link?' pins the decision it supports.

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?

The opening question establishes a clear use context (pre-click / pre-signature / pre-payment vetting) and it names the x402 payment path plus a sibling (get_example) for a free sample. It stops short of explicit exclusions — it never says to use site_audit for page content or domain_intel for registry data instead.

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