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

No annotations are provided, so the description carries the full burden, and it does meaningful work: it discloses the operational footprint ('read-only DNS plus one GET of the public MTA-STS policy file') and that output includes warnings on weak/missing configuration. It omits any note on rate limits, failure modes when the MTA-STS policy file is unreachable, or caching behavior.

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?

Two sentences, front-loaded with the verb and resource, then the record breakdown, then the behavioral disclosure. No filler or redundancy; every clause carries 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?

With no output schema, the description must tell the agent what comes back, and it does: enforce/testing mode, max_age, MX for MTA-STS, reporting address for TLS-RPT, logo + VMC for BIMI, plus warnings. Nothing critical for correct invocation or interpretation is missing.

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 a single 'domain' parameter with a 100% schema description, so the schema already does the work. The description only refers to 'a domain's' records without adding format, TLD, or subdomain-handling semantics, which is the expected baseline when coverage is complete.

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 (report) and resource (a domain's modern email-security records) and enumerates the exact record types covered: MTA-STS, TLS-RPT, BIMI. The phrase 'beyond SPF/DMARC/DKIM' cleanly separates it from siblings like spf_check, dmarc_check, and dkim_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?

The 'beyond SPF/DMARC/DKIM' framing tells the agent this tool complements rather than replaces the SPF/DMARC/DKIM siblings, and the mention of warnings hints at triage use. However, it never gives an explicit when-to-use or when-not-to-use directive (e.g. 'run this after dmarc_check to surface modern-record gaps').

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