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

The annotations already declare read-only, idempotent, open-world, non-destructive behavior. The description adds material context beyond those hints: pricing at $0.010 per call, no charge for unknown domains returning 404, and per-field source/confidence values.

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 description is front-loaded with the core question and returned-field categories, then adds pricing, a sample, and return shape. The return list is long but justified because there is no output schema; there is minor duplication between the prose field list and the Returns line.

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 Returns line is necessary and covers all major response categories. The description also discloses failure behavior, cost, and confidence/source metadata, making it complete for a one-parameter read-only lookup.

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 domain parameter is fully documented with a bare-domain example. The description supplies a sample invocation but adds no new syntax, format, or constraint 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?

The description states a specific lookup question, 'Who runs this site?', and enumerates the company facts returned, so the resource and scope are clear. It does not distinguish itself from sibling domain/company-intelligence tools such as domain_profile or domain_whois, which prevents 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 opening question implies when to use the tool, and the 'unknown domains answer 404 and are not charged' note covers a failure case. However, it never says when to choose this tool over alternatives like domain_profile, domain_whois, or brand_lookalikes, leaving sibling selection to inference.

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