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

While annotations declare readOnlyHint=true, the description adds critical behavioral nuance: it explains that next_record is null when blocked, and that 'THAT NULL IS AN ANSWER: relay the blockers and never compose a stronger record to fill the gap.' It also mandates presenting the record verbatim and requiring human approval, plus notes 'Requires an API token.' These details go well beyond the annotation safety profile.

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 dense but every sentence earns its place. It front-loads the core purpose, then explains return fields, null semantics, usage caveats, and approval requirements without repetition or filler. The structural flow is logical and efficient.

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?

The tool is conceptually complex (readiness verdict, blockers, null handling, human approval), yet the description covers the full context: what it returns, what null means, how to handle the record, when to use it, and the required authentication. With an output schema also present, this description is complete for correct invocation and handling.

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 coverage is 100%: the domain parameter description already explains it must be a 'VERIFIED monitored domain' and that ownership is not disclosed. The tool description reinforces 'ONE domain' and 'caller's account monitors' but adds no new semantic meaning beyond the schema. Baseline 3 is appropriate when the schema does the heavy lifting.

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: 'Read the DMARC enforcement-readiness verdict for ONE domain the caller's account monitors.' It clearly distinguishes this from sibling tools like scan_domain by emphasizing the evidence window and the readiness verdict, noting that 'only this evidence window can say whether tightening it would start rejecting real mail.'

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?

Explicit guidance is provided: 'Use this before proposing enforcement' and contrasts with scan_domain ('a scan can show a domain's current policy, but only this evidence window can say whether tightening it would start rejecting real mail'). It also gives strong when-not-to instructions: 'never compose a stronger record to fill the gap' and 'a human must approve it before it is published.'

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