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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive), and the description adds genuinely non-obvious context: checks run in parallel, output includes score/letter grade/maturity stage/prioritized findings, and the subtle scoringModelVersion vs dnsChecksPackageVersion distinction with an explicit warning that a lower model version is expected, not a gap. The scoringConfigHash citation guidance is real operational value beyond structured data.

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?

Purpose, aggregation scope, use cases, then versioning notes — well front-loaded. The version-stamp passage runs long and reads more like output documentation than tool-selection guidance, but every sentence contributes factual content rather than filler.

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 correctly enumerates return value shape (score, 6-band grade, maturity stage, prioritized findings) and the version/hash fields an agent needs to cite results. The remaining gap is sibling routing — it never says to prefer the individual check_* tools or batch_scan when those fit better.

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 schema already carries domain, format, profile, and force_refresh semantics, including enums. The description adds only indirectly, via 'scan-included check' hinting that profile determines check inclusion; it gives no format/profile guidance of its own, 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?

Opens with a specific verb and resource ('Run a full DNS and email security audit for a single domain') and immediately scopes it against the many check_* siblings by naming the checks it aggregates. An agent can tell this is the umbrella single-domain audit rather than a granular check or a batch operation.

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?

Explicitly states three good use cases: comprehensive single-domain audit, overall security grade, and email-security maturity assessment. It does not, however, explicitly route the agent away from alternatives (e.g., use check_spf for one check, batch_scan for many domains), leaving the boundary with siblings implied.

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