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

Annotations already establish the safe read-only profile (readOnlyHint=true, destructiveHint=false, openWorldHint=true). Beyond that, the description discloses a genuine behavioral trait structured data does not: the $0.002 USDC cost on Base, plus an implicit latency hint ("Instant"). It still omits payment flow and error behavior, so it is not fully rich.

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?

Two tight sentences with no filler; the functional scope is front-loaded and the cost follows. Every clause carries information the agent needs.

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?

An output schema exists, so return values need not be explained, and the description plus annotations cover safety and scope for a low-complexity one-parameter tool. Minor gaps remain: no mention that 'url' is not marked required and no guidance on payment handling.

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 the single 'url' parameter is already documented as "Destination URL to inspect." The description adds no format, syntax, or validation detail (e.g., scheme requirements) beyond the schema, 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?

The description names a specific verb (audit), the resource (URL), and enumerates the exact threat classes checked: phishing, unicode homograph, redirect loop, and hidden-DOM prompt injection. The scoping to URLs distinguishes it from prompt- or calldata-focused security_* siblings.

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: an agent can infer you call this to vet a URL before visiting or feeding it onward. There is no explicit when/when-not guidance, no named alternative (e.g., security_prompt_firewall for raw prompt text), and no prerequisites stated.

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