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

Annotations already declare readOnlyHint/idempotentHint/openWorldHint, but the description goes further by specifying exactly what is touched ('only queries public DNS and the domain's public MTA-STS policy file') and how the result is computed (weighted breakdown capped at 100). It omits any note on rate limits or caching, which keeps it short of a 5.

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 lead sentence front-loads the core action, and the scoring detail is parenthetically packed rather than spread across extra sentences. It is dense but every clause carries information; only the long second clause risks being hard to scan.

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?

With an output schema present, the description needn't restate return values, yet it still previews the shape of the result (score, grade, per-check findings, report link). Combined with rich annotations and full schema coverage, an agent has everything needed to invoke it correctly.

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 description coverage is 100%, and all three parameters — domain, dkim_selector, include_raw — are fully documented in the schema itself. The description adds no parameter-level meaning beyond that, 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?

The description opens with a specific verb and resource: 'Audit the email-authentication DNS records of a domain.' It further enumerates the record types covered (SPF, DKIM, DMARC, BIMI, MX, MTA-STS, TLS-RPT) and the scoring model, leaving no ambiguity about what the tool produces.

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 clearly establishes the context of use (auditing a domain's email auth posture) and notes the same engine backs the DnsGuard JSON API, which helps an agent reason about equivalence. There are no sibling tools and no explicit when-not guidance, but for a standalone tool the trigger condition is unambiguous.

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