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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and destructiveHint, and the description reinforces by saying 'Read-only — no domain mutation, no destructive side effects'. It adds useful context beyond annotations, such as speed (~3-8s) and detailed output structure (grade, score, issue list, recommendations, citation URLs), and explicitly states 'No auth'.

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 concise and front-loaded: two sentences total. The first sentence covers purpose and outputs, the second covers alternatives and follow-ups. No redundant words; every clause adds value.

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?

Despite having no output schema, the description enumerates return elements (letter grade, numeric score, structured issue list, prioritised recommendations, result sections, citation URLs). It also covers usage context, speed, safety, authentication, and alternative tools. For a single-parameter tool with rich annotations, this is fully complete.

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?

There is only one parameter, domain, and the schema description already provides thorough coverage (100%) including format guidance ('Domain name only, e.g. example.com'). The description doesn't add parameter-specific semantics beyond what the schema covers, so 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 clearly states the action: 'Run the fast IntoDNS.ai DNS and email security scan'. It specifies the resource (DNS and email security) and distinguishes from siblings by mentioning alternatives like get_everything_report and start_deep_scan.

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?

Explicit guidance is provided: 'The default tool for agent-visible scan evidence' and alternatives are named with their specific advantages (deeper single-shot report, Internet.nl-grade analysis). Post-scan steps are also suggested: 'use explain_issue or generate_dns_fix on any returned issue'.

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