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

With no annotations, the description carries the behavioral burden. It clearly indicates a read-only DNS-based analysis and states the output format (A-F grade with findings). It could mention limitations/rate limits, but the 'from its public DNS' phrasing sufficiently implies no domain mutation.

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 core information is front-loaded in two efficient sentences: what it grades, how it grades, and what it returns. The trailing 'Free tool by Postbox Services' sentence adds little for tool selection or invocation, preventing a 5.

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 simple one-parameter tool with no output schema, the description is complete enough: it names the input domain, the method, and the returned grade/findings. It could elaborate on the findings structure, but nothing essential for a correct call is missing.

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 coverage is 100% and the single 'domain' parameter is already documented with an example. The description adds contextual meaning about DNS checks but no additional parameter syntax or formatting details, so the baseline 3 applies.

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 ('Grade') and resource ('domain... exposed to email spoofing and BEC') with clear method details (SPF, DMARC, alignment, lookalike domains). The A-F grade output distinguishes it from sibling tools like check_blacklist and whois_lookup without ambiguity.

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 intended use is implied: evaluate a domain's spoofing/BEC exposure. However, the description does not explicitly say when to prefer this tool over siblings or when not to use it, leaving selection partly to inference.

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