email_dns_check

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

With no annotations, the description carries the burden and does real work: it discloses that MX targets must resolve and must not be CNAMEs, that SPF include:/redirect= expansion is performed and lookup/void limits are counted with permerror consequences, and that DMARC policy, pct and rua are extracted. It stops short of stating that the tool is purely read-only or noting query volume/resolver rate considerations.

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?

Four tight sentences, front-loaded with the scope and followed by the per-record behavior that matters most. Every clause carries information about what will be checked or what will fail; nothing is padding.

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?

An output schema exists, so return-value explanation is not required, and the description covers the diagnostic surface (MX, SPF limits, DMARC fields, DKIM selectors, MTA-STS/TLS-RPT) adequately for an agent to predict results. The only real hole is the undocumented `resolver` parameter and the absence of any note on query cost or timeout behavior.

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 0%, so the description must compensate. It does well for `selectors`, explaining the comma-separated format, giving an example ('mail2024,s1'), and justifying why the caller must supply them because selectors are arbitrary. `domain` is self-evident, but `resolver` (defaulting to 'system') is never mentioned, leaving one of three parameters opaque.

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 a domain's email DNS,' then enumerates exactly which records (MX, SPF, DMARC, DKIM, MTA-STS). That enumeration cleanly separates it from the generic dns_lookup and from http_check/tls_check siblings without needing to name them.

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?

Usage is only implied by the record scope; there is no explicit statement of when to reach for this over dns_lookup or when a single-record lookup would suffice. The one concrete directive is about supplying DKIM selectors, which is operational guidance rather than tool-selection guidance.

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