Audit email authentication

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

Annotations already declare readOnly, idempotent, non-destructive, and openWorld, so safety is largely covered. The description adds real value beyond them: the no-mail-server-connection constraint narrows what 'open world' means here, the 'Returns a score with fixes' statement supplies return-value context despite no output schema, and the untrusted-data/prompt-injection warning is a meaningful operational caveat. Rate limits or failure behavior are not covered.

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?

Front-loaded with the audited surface, then use cases, then behavioral caveats — a logical order with no filler. Each clause (lookup limit, selector probing, no server connection, untrusted data) carries distinct information.

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 three-param read-only tool with no output schema, the description covers what is checked, when to invoke it, what it returns at a high level, and the safety/untrusted-input posture. Everything an agent needs to select and call it correctly is present.

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%, so the baseline is 3. The description references 'any you give' for DKIM selectors and mentions MTA-STS record/policy file, loosely mapping to the optional params, but adds no syntax, format, or default details beyond what the schema already documents.

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 and resource ('Audits a domain's email authentication from public DNS') and enumerates the exact checks performed (MX, SPF with 10-lookup limit, DKIM selectors, DMARC, MTA-STS, TLS-RPT). This cleanly separates it from sibling tools like dns_lookup, tls_inspect, and security_headers, which each cover only a fragment of this surface.

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?

Gives concrete triggering scenarios: 'mail goes to spam', spoofing concerns, and after mail-server migrations. It also states what it does NOT do ('It never connects to a mail server'), which implicitly distinguishes it from a mail-server-side check. It stops short of naming an explicit alternative tool for narrower checks, so it is clear context rather than full when/when-not routing.

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