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

The annotations already declare readOnlyHint, idempotentHint, openWorldHint, and destructiveHint=false, so the safety profile is covered. The description adds what data is returned but does not disclose limitations such as rate limits, caching, auth needs, or behavior when RDAP data is unavailable.

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?

The description is three compact sentences with no wasted words: purpose and returned fields first, then the security rationale, then the parameter clarification. It is appropriately sized and front-loaded.

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 one-parameter read-only tool with an output schema and full annotations, the description covers the purpose, returned content, and the meaning of scan_id. It omits explicit guidance on when to prefer this tool over related domain-history or DNS tools, but otherwise provides enough to invoke it correctly.

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 0% for the single scan_id parameter, so the description must compensate. It does so by explaining that scan_id is the UUID of a ScanMalware scan, which clarifies the value's source and format beyond the bare schema type.

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 names a specific verb ('Get') and resource ('registration data (RDAP)') and enumerates the returned fields (registrar, registration/expiry dates, domain age, nameservers, status). It scopes the lookup to 'the scanned domain and its IP addresses,' which helps distinguish it from generic domain tools, but it does not explicitly name a sibling alternative to route against.

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 phrase 'A very young domain is a common phishing signal' implies the tool is useful for phishing assessment, giving some usage context. However, it does not state when to choose this over alternatives such as get_domain_history or get_domain_stats, nor does it provide any exclusions or prerequisites.

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