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

Beyond the readOnlyHint annotation, the description reveals the surprising behavior that the tool returns a LIST and that ten IDs carry two records due to differing ICANN/IANA name spellings, with both records returned rather than one chosen. This is valuable, non-obvious behavioral context an agent needs before invoking the tool.

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?

Two dense, well-structured sentences: the first front-loads the complete data scope, and the second adds the critical duplicate-record caveat. There is no filler or redundancy; every clause earns its place.

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 read-only single-parameter lookup with an output schema and safety annotations, the description is complete: it states what is returned, scopes the request, and flags the main edge case (duplicate records). Nothing an agent needs to call it correctly is missing.

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?

The input schema already fully documents the single iana_id parameter with examples. The description reinforces that the ID is the lookup key but adds no new parameter-level detail, so the baseline score of 3 is appropriate.

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 clearly states the tool fetches the full record for a single IANA registrar ID, enumerating the specific data returned: accreditation status, RDAP base URL, and enforcement notices. It is unambiguous in scope (one ID) but does not explicitly differentiate itself from sibling tools like list_enforcement_actions or resolve_registrar.

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 scope 'for one IANA registrar ID' implies this is the per-ID lookup, but the description never states when to prefer it over alternatives such as list_enforcement_actions, resolve_registrar, or verify_quote. There is no explicit when/when-not guidance or exclusion, only an inferable use case.

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