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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint and destructiveHint=false, so the safety profile is covered. The description adds genuine value about the underlying data sources (RDAP, MX/SPF/DMARC) and their interpretation as fraud signals, but says nothing about rate limits, failed or unresolvable lookups, or freshness of the records.

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?

One compact sentence that front-loads the returned data categories before the interpretive note. Nothing is padded, though it is a noun phrase rather than a verb-led statement of action.

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?

With no output schema, the description carries the burden of describing the response, and it does so by listing the four data families returned. For a single-parameter read-only lookup that is nearly sufficient; only error behaviour and result formatting are unaddressed.

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 parameter already documents that it accepts 'Domain, URL, or email address'. The description adds no additional input semantics beyond what the schema states, so the baseline of 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 resource (a domain) and enumerates exactly what is retrieved: registration date, age, registrar via RDAP, and email-auth records (MX, SPF, DMARC). That is far more informative than a bare 'look up a domain'. It stops short of explicitly contrasting itself with siblings like company_profile or due_diligence_report, so it earns a 4 rather than a 5.

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 trailing clause 'which are common fraud signals' hints at a fraud/vetting context, but no sentence says when to reach for this tool, when to prefer a sibling such as company_profile or screen_sanctions, or what prerequisites exist. Usage is left almost entirely to inference.

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