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

Annotations already declare readOnly/openWorld/idempotent/non-destructive, and the description adds real behavioral context beyond them: SMTP transport TLS cannot be observed from DNS, so a DNS-only run tops out at INDETERMINATE which is not a pass. This discloses a genuine result limitation. It does not mention caching behavior beyond force_refresh or rate limits.

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?

Three tight sentences, front-loaded with the core verdict purpose, then the control list, then the DNS limitation and sibling differentiation. No filler; each sentence carries decision-relevant 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 carries the return burden and does so: it lists all six controls and the three verdict states (satisfied / not satisfied / NOT MEASURED) plus the INDETERMINATE ceiling. An agent knows what it will get and the limits of that result.

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 documents domain, format, and force_refresh. The description reinforces the single-domain constraint ('ONE domain') but adds no syntax or format detail beyond what the schema provides, 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+resource+scope: 'Answer, for ONE domain, whether it meets the New Zealand SGE requirements.' It enumerates the six controls it evaluates and explicitly distinguishes itself from map_compliance, so an agent can route correctly without opening the schema.

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 scopes to ONE domain and names the sibling it is not (map_compliance), which clarifies when this aggregate verdict tool is preferred over a compliance-mapping tool. It stops short of telling the agent when to reach for the single-control siblings (check_dmarc, check_spf) instead.

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