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

With no annotations, the description carries the full disclosure burden. It does reveal what is fetched (WHOIS, several DNS record types, an SPF/DMARC audit), which is useful behavioral context, but says nothing about read-only safety, rate limits, latency, caching, or how a nonexistent or malformed domain is handled.

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?

Three sentences, zero filler: what it returns, when to use it, then the parameter toggles. The information is front-loaded with the payload contents before the usage advice.

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?

For a three-parameter lookup with no output schema and no annotations, the description covers the essentials an agent needs to decide and invoke: contents, purpose, and toggle semantics. It would be fully complete with a note on failure behavior for unresolvable domains or the response's structure, but nothing critical 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 0%, so the description has to compensate, and it does: it explains that include_dns and include_security 'toggle the two halves' of the output, mapping each boolean to a distinct result section. The remaining 'domain' parameter is self-evident from its name, though defaults (true/true) are not restated in prose.

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 operation (WHOIS + DNS + SPF/DMARC audit) against a specific resource (a domain), and even enumerates the record types returned (A, MX, NS, TXT). It is immediately distinguishable from siblings like lookup_company, lookup_financials, or extract_contacts, which operate on other entity types.

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 two concrete use cases — profiling a company's web estate and checking email posture — which tell the agent when this tool is the right pick among the company-oriented siblings. It stops short of naming an explicit alternative or stating when not to use it, so it does not reach the top of the scale.

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