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

Annotations already declare readOnly, idempotent, openWorld and non-destructive, so the safety bar is low. The description adds real value beyond that: a stated cost (1 credit per call), the absence of personal contact data, and the shape of the normalised record returned.

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?

Three short, front-loaded clauses cover scope, cost and output format with no filler. The cost and output statements are compact but each carries decision-relevant information.

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 description responsibly sketches the return value ('normalised registration record: domain, IP network or autonomous system') and discloses cost and privacy limits. Only a fuller account of the record fields or error behaviour 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?

Schema description coverage is 100% and both parameters (query format examples, fields enum semantics) are fully documented in the schema. The description only restates the accepted query types, adding no syntax or defaulting detail beyond the structured fields, 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 ('look up the public registration record') plus the accepted input types (domain, IP, AS number) and the RDAP source. An agent can tell it is not a generic DNS/IP tool, but the description never explicitly contrasts itself with the sibling tools dns_lookup and ip_lookup, which overlap in input domain.

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 only implied: the credit cost, the 'without personal contact data' caveat and the record types suggest when the tool fits. There is no explicit when-to-use vs when-not-to-use guidance and no named alternative for DNS/RDAP-adjacent lookups, so the agent must infer routing.

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