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

Beyond the readOnlyHint/openWorldHint annotations, it discloses the pricing model (per site, via x402), the billing exception ('not charged if no site can be checked'), and the full shape of each result including verdict, score, and per-flag evidence. It also points to list_prices for current pricing, which is exactly the kind of context annotations cannot carry.

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-loads the core capability, then layers cost, output shape, use case, and billing caveat in a tight sequence with no filler. Every sentence contributes distinct 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?

No output schema exists, yet the description enumerates the return payload (verdict, 0-100 score, TLS/redirect/header/mixed-content/insecure-form/domain-age flags, summary count) and the billing and referral path. Nothing an agent needs to invoke or interpret the tool 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 description coverage is 100% and there is a single parameter, so the schema already documents urls fully. The description's note that pricing is per unique URL is a useful but minor addition beyond the schema's own text, so the 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?

States a specific verb and resource ('batch website safety check... full /safe report for several URLs in one call') and implicitly contrasts with single checks by noting it is cheaper than them. An agent can distinguish this from check_site_safety without opening the schema.

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 a concrete use case ('screening every link in a search result, email, or document at once') and a cost-based reason to prefer it over single checks. It does not name check_site_safety or check_site_safety_pro as alternatives, so the routing guidance is implied rather than explicit.

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