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

With no annotations, the description carries the burden and does well: it discloses that no API key is required, that results are a limited preview, and precisely which fields the paid tier adds on top. It omits rate limits, read-only/vs cached behavior, and any failure mode for an invalid or apex-only domain.

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 preview scope and returned signals are front-loaded in the first clause, with the upsell to the paid tool last, which is the right ordering. It is dense but each clause carries information, though the paid-tier feature list is long enough to drift toward marketing copy.

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?

No output schema exists, and the description compensates by naming the concrete return fields, which is the key missing piece. Rate limits, quota, and an invalid-domain failure path remain undocumented, a modest gap for a trivial single-parameter read.

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 already documented with an example and apex hint. The description only repeats 'company domain' without adding format, normalization, or validation guidance 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?

States a specific verb and resource (keyless DNS/RDAP enrichment preview for a company domain) and enumerates exactly which signals it returns: MX provider, TXT SaaS, RDAP age/registrar. It also distinguishes itself from the paid /company/enrich, so an agent can tell what this tool does and does not produce.

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?

Clearly frames itself as a free, keyless preview and routes to get_premium_access for the full record, so the free-vs-paid choice is explicit. It does not mention when to prefer the sibling resolve_company or search_jobs, leaving one routing decision unstated.

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