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

With annotations present the bar is lower, and the description still adds real context beyond them: the probe is 'bounded', provider uncertainty is disclosed, cost is $0.003 USDC per successful call, and the excluded capabilities are named. The one tension is that annotations set readOnlyHint=false while the description frames this purely as a resolution/read operation — a likely conservative default rather than an explicit contradiction, but worth flagging as unexplained.

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 tight sentences, front-loaded with the core action and facets, then scope exclusions, then the price. No filler, though 'Provider uncertainty is explicit' is slightly abstract and could be folded into the probe clause.

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 single-parameter, no-output-schema tool this covers the essentials: what is queried, which sources are used, what is deliberately not returned, cost model, and reliability caveats. Return shape is undescribed but the enumerated facets give the agent a working expectation.

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?

Only one parameter, and schema description coverage is 100% ('Bare DNS domain name, not a URL, path, IP address or email'). The description's 'bare public domain' reinforces this but adds no syntax, normalization, or IDN guidance beyond the schema, so the 3 baseline 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 ('Resolve') and resource ('bare public domain') and enumerates the exact output facets: registration, DNS, HTTPS/TLS and mail-policy state, plus the data sources (RDAP, DNS, MX/TXT/SPF/DMARC, TLS probe). This is enough for an agent to distinguish it from every listed sibling, none of which operate on domains.

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 description implies usage ('Resolve a bare public domain') and deliberately fences the scope with 'No registrant personal data, vulnerability scanning, mailbox existence or deliverability claim', which tells the agent what requests are out of bounds. However, it never states when to reach for this tool versus another (e.g., package_preflight for packages) or any prerequisite conditions, so usage is only implied.

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