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

Despite strong annotations (readOnly, idempotent, non-destructive), the description adds crucial behavioral context: next_record is null while blocked, null is itself an answer, agents must not compose a stronger record, returned records must be presented verbatim, and human approval is required before publishing. It also warns that unmonitored domains are refused without disclosing ownership.

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?

The description is front-loaded with the primary use case and remains dense without wasted words. Each sentence earns its place: usage, verdict scope, return fields, null semantics, record handling, and differentiation from scanning.

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 single-parameter tool with a rich input schema, full annotations, and an output schema present, the description covers everything the agent needs: when to call it, what it returns, what the null case means, and the safe workflow. Nothing essential 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?

Schema description coverage is 100% and the schema already thoroughly documents the domain parameter, including verified monitored domain requirement and not-found behavior. The tool description reinforces 'ONE domain' but does not add meaning beyond the schema's parameter documentation, so the baseline of 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?

The description names a specific verb and resource: 'Read the DMARC enforcement-readiness verdict for ONE domain the caller's account monitors.' It clearly differentiates from the sibling scan tool by saying a scan can show current policy but only this evidence window can judge readiness.

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?

It explicitly states when to use the tool ('when a signed-in operator asks whether a monitored domain is ready for the next DMARC step') and when it is the right choice before proposing enforcement. It also contrasts with scan_domain, explaining that only this tool's evidence window can determine whether tightening would reject real mail.

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