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

Beyond the annotations (readOnly, idempotent, openWorld), the description discloses the real behavioral traits: cached sites return instantly, uncached sites trigger an on-demand scan of 20-60 seconds, and after ~25 seconds the result may come back with status "generating" plus retry_after_seconds. That latency and partial-result behavior is exactly what an agent needs to plan around, and the annotations don't carry it.

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?

The core purpose and the payload come first, the usage triggers follow, and the latency caveat comes last. The middle sentence is long and list-heavy, but each clause, including the list of underlying checks, earns its place by helping the agent judge relevance.

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?

The tool has an output schema, so return values needn't be explained, yet the description still flags the "generating" status and retry_after_seconds so the agent isn't blindsided. With latency, input format and scope all covered, nothing needed in order to call it 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 coverage is 100% and the single parameter is fully documented in the schema, including the bare-domain-or-URL form and the fact that only the hostname is assessed. The description restates "Accepts a bare domain or any URL" rather than adding new meaning, 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 ("Look up") and resource ("verified.fyi's independent trust report for a website"), and it spells out the payload: a 0-100 trust score, verdict, summary and full-report link. This makes it unmistakable from the only sibling, list_research, which does something unrelated.

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?

It gives concrete trigger conditions: before visiting, buying, signing up, entering payment details, or when someone asks whether a site, shop, link or sender's domain is legitimate. It gives no explicit when-not or named alternative, but the use cases are stated clearly enough that an agent can tell when to reach for it.

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