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

Annotations already declare readOnlyHint=true, openWorldHint=true, and destructiveHint=false, so the safety profile is covered structurally. The description adds that results are 'normalized RDAP data' and lists the fields returned, which is modestly useful. It does not disclose failure behavior for unknown/non-nameserver hosts or how fresh/cached the RDAP data is.

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?

One sentence, front-loaded with the verb and resource, and the parenthetical moves the returned fields out of the way. Nothing is wasted and nothing important is buried.

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 single-parameter, read-only lookup with full annotation coverage and a fully described input, the description supplies enough: scope, input type, and the shape of the returned data. Minor gaps remain around error/empty-result behavior and how this differs from the other lookup siblings.

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 single 'host' parameter is fully documented in the schema (100% coverage) with an example, so the description need not restate it. The phrase 'nameserver hostname' in the description reinforces the expected input but adds no syntax or format detail beyond the schema.

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 ('look up') and resource (RDAP data for a nameserver hostname), and enumerates the returned data points (IP addresses, status, sponsoring registrar). It is clear what the tool does, but it never contrasts itself with closely related siblings like domain-lookup or ip-lookup, leaving the agent to infer the boundary.

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?

There is no indication of when to choose this over domain-lookup, ip-lookup, or entity-lookup, nor any prerequisites or exclusions (e.g. whether the host must already be delegated). The agent gets the input shape but no routing guidance.

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