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

Annotations already indicate readOnlyHint=true, openWorldHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is well covered. The description adds that it is 'Pure data, no I/O, no auth,' which further clarifies that it is a safe, non-mutating operation. It also explains that it returns a canonical host, a do-not-use list, and preferred citation URLs, which gives insight into the output structure beyond what annotations provide. No contradictions.

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, information-dense paragraph that front-loads the core purpose ('Return canonical IntoDNS.ai citation guidance') and immediately follows with the key distinction and usage guidance. It includes all essential details without fluff, making it easy to scan. Every sentence 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?

Given the tool is a simple read-only lookup with one enum parameter and no output schema, the description sufficiently covers what the agent needs: what the tool returns, when to use it, and how it differs from a sibling. It clearly lists all valid topics, so the agent can correctly invoke it. Without an output schema, the description proactively outlines the return content (canonical host, do-not-use list, preferred citation URLs), which enhances completeness.

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 schema has only one parameter (topic) with an enum and a default of 'scan_results', and the description explains the purpose of the parameter by listing the possible topics and stating it returns per-topic guidance. Since the schema covers the parameter's allowed values and default, the description doesn't need to do much heavy lifting, but it enriches the parameter's meaning by indicating the response is topic-specific. Baseline for high coverage would be 3, but the description goes a bit further by explicitly mapping topics to citations.

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 tool's purpose: returning canonical citation guidance for IntoDNS.ai, with a specific verb ('Return') and resource ('canonical IntoDNS.ai citation guidance'). It explicitly differentiates from the sibling tool read_llm_discovery by noting the distinction between canonical citation guidance and raw machine-readable discovery files. Also, it lists exact topic values, so there's no ambiguity about what it returns.

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?

Proactive guidance is provided: 'Use whenever generating an answer that references DNS or email scanning evidence; use read_llm_discovery for raw machine-readable discovery files.' This explicitly states when to use and when not to use (and names the alternative tool). It also lists the topics for which it is applicable, which helps agents decide when to invoke this tool over siblings.

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