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

Annotations already declare readOnly, idempotent, non-destructive and open-world, so the safety profile is covered. The description adds genuinely useful behavior beyond that: a 24-hour shared cache with audit_ownership, a 0-100 control score, per-layer reasons plus 'first step to take control,' and raw registration facts. It does not mention rate limits or failure modes, but adds solid context.

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?

Front-loaded with the verb and the fact inventory, then the return shape and cache note. The long enumeration costs some density, but each clause names a distinct deliverable and nothing is redundant 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 annotations covering safety, the description carries the return-value burden and does so by specifying the score, per-layer reasons, action step, and raw facts. What it lacks is guidance on interpretation thresholds or how the score is derived, which an agent scoring control would find useful.

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 both parameters are documented in the schema, so the baseline is 3. The description adds only an indirect hint that registrant data may be compared (relevant to business_name) and nothing about domain format beyond what the schema already says.

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 (check) and enumerates the exact resources and facts covered: registrar/IANA id, registrant, EPP status, dates, DNSSEC, nameservers, mail provider from MX/SPF. This is far beyond a tautology. It only partially differentiates from audit_ownership, mentioning it solely as a cache sharer rather than as a distinct alternative.

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?

Usage is implied via 'without reading the website,' suggesting this is for situations where crawling is unwanted, and the shared-cache note hints at a relationship with audit_ownership. However, there is no explicit when-to-use/when-not-to-use statement or rule for choosing between this and audit_ownership.

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