check_email_deliverability

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

No annotations are provided, so the description must fully disclose behavior. It states it resolves real DNS live, returns verdicts and fixes, and mentions the deep parameter behavior (slower). It does not mention side effects, but the operation is a read-only check.

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 paragraph but is well-structured: first states purpose and verdict types, then use cases, then return values. No filler, but could be split for readability. Still efficient.

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 no output schema, the description adequately explains the return values (HEALTHY, NEEDS_ATTENTION, AT_RISK with score and fixes). It covers purpose, usage, parameters, and behavior completely.

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?

With 100% schema coverage, baseline is 3. The description adds context that deep involves probing common DKIM selectors and is recommended for full checks, which is useful beyond schema descriptions.

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 checks a domain's email authentication and DNS health (SPF, DKIM, DMARC, MX) and returns a deliverability verdict. The action is specific (check) and the resource is a domain. Use cases are listed.

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 explicitly lists four use cases: setting up sending, debugging spam, vetting a domain, and checking bulk-sender requirements. No exclusions or alternatives are given, but no sibling tools exist, so guidance is sufficient.

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