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

With no annotations, the description must carry the full behavioral burden. It does describe the audit checks and that results are 'graded A-F with fixes', which is useful, but it never explicitly states that the operation is read-only, non-destructive, or that it queries public DNS records. The term 'audit' implies safety, but the lack of explicit confirmation leaves a gap.

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 efficient sentence that front-loads the core action ('Email authentication audit of a domain') and then supplies a compact list of checked components. Every clause adds relevant information with no wasted words.

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 presence of an output schema, the description need not explain return values and correctly focuses on what is checked and the use case. It covers the major checks, grading, and fixes, but it omits any note about network dependencies or expected latency for a multi-record DNS audit, which would be helpful context.

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 one parameter ('domain') with 0% schema description coverage. The description says the audit is 'of a domain', which clarifies what the parameter represents, but it does not specify format (e.g., bare domain vs. URL) or give an example. This is the minimum viable compensation for the missing schema description.

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 gives a specific verb and resource: 'Email authentication audit of a domain', then enumerates exactly which records and policies are checked (MX, SPF, DMARC, DKIM, MTA-STS, TLS-RPT, BIMI). This is clear enough for an agent to know what the tool does, though it does not explicitly contrast with sibling tools like email_validate or dns_lookup.

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?

It provides a clear use case: 'Use for deliverability and phishing-risk checks.' That tells the agent when to reach for this tool, but it does not name an alternative or state when not to use it, so it falls short of the explicit routing seen in top-tier definitions.

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