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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint, so the safety profile is covered. The description adds meaningful behavioral context beyond that by explicitly stating the monetary cost of 0.0005 XNO and the x402 payment mechanism, which is important for invocation.

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 a single, compact sentence that front-loads the core purpose and then lists the exact data categories. The cost/payment sentence is also concise and provides necessary operational information without waste.

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 tool with a detailed input schema, an output schema, and annotations covering read-only/idempotent behavior, the description is complete. It adds the only missing operational detail: the fee and payment method.

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 the parameter description already explains that 'domain' is a domain name and which lookups will be performed. The tool description adds no additional parameter-level insight, so the baseline 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 names a clear resource (domain) and enumerates specific data categories: DNS records, WHOIS registration, SSL/TLS certificate, HTTP headers. This immediately distinguishes it from sibling tools like geoip_lookup or check_url_status.

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 description implies the tool should be used when comprehensive domain intelligence is needed, and the component list gives context. However, it does not explicitly state when to prefer this over siblings or mention any exclusions, such as when check_url_status or geoip_lookup would be more appropriate.

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