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

Goes well beyond the readOnly/idempotent annotations by disclosing pricing (USD 0.002), a free tier shared across several lookup tools, latency (0.3-2 s), the 422-not-charged case for private/reserved addresses and non-RDAP TLDs, redaction handling via `redacted` fields, and an untrusted-data warning. This is exactly the behavioral context an agent cannot get from 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?

Dense but front-loaded: the purpose and input format come first, then return fields, then error/cost behavior. Nearly every clause carries information, though it is a long single block that could be split for scannability.

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 compensates by enumerating the returned fields for domains and for IP/AS queries, plus null/redaction semantics. Combined with cost, latency and error behavior, an agent has everything needed to invoke and interpret the call.

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 single `query` parameter is already documented with the same examples in the schema, so the description adds no syntax or format detail beyond it. Baseline 3 applies when the schema carries the parameter burden.

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 (RDAP/whois registration lookup) and enumerates the three accepted query kinds (domain, IPv4/IPv6, AS number). It also spells out what each query type returns, so an agent can distinguish it from sibling lookups without opening the schema.

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 through the input taxonomy and the 'found:false vs 422' rules, which tell the agent when a result is absent versus invalid. However, it never names alternatives such as ip_lookup or inspect_domain or states when to prefer one over the other, 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.