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

Annotations already declare readOnly/openWorld/non-idempotent, but the description adds genuinely new operational context: data provenance ('public DNS, RDAP and the home page only'), pricing ($0.01/call via x402 USDC or card key, first 25 free, failed calls free), and the key consequence that each repeat call is billed, which is exactly why idempotentHint=false matters here. This is behavior an agent cannot derive from the structured fields.

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 output inventory is front-loaded in the first sentence and the cost/safety caveats are packed into the tail, so the important facts land early. The middle enumeration is dense and long but each item describes an actual returned field, so nothing is clearly padding.

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 and no sibling differentiation available from annotations, the description carries the full burden and does: it lists the returned data, the data sources, the billing model, and confirms no side effects. An agent can decide to call it and predict the cost and result shape without further information.

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 schema already documents that a URL is accepted and its host used, so the baseline is 3. The description adds only a light example ('domain=stripe.com') and the phrase 'any domain', which adds marginal clarity rather than new semantics.

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 states a concrete capability ('Company enrichment in one call for any domain') and enumerates the exact data returned: site name/description/logo, tech stack, email provider and SPF/DMARC, hosting IP holder, DNS records, registrar, age, expiry. An agent knows precisely what comes back, which matters since there is no output schema. It does not distinguish itself from overlapping siblings such as domain_report, dns_lookup or company, so it stops short of 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?

It names concrete use cases ('lead enrichment, company research, vendor checks or sales prospecting') and supplies a worked example (domain=stripe.com). However it gives no exclusions and no routing advice against the many similar siblings (domain_report, dns_lookup, pack_website_audit), leaving the agent to guess when this bundle is preferable to a single-purpose lookup.

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