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

Annotations already establish readOnlyHint, idempotentHint and destructiveHint=false, so safety is covered. The description adds real context beyond that: beta status, the exact report payload sections, and the important caveat that preview imports produce no stored report. Retention period and whether reports expire are not stated.

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 beta marker, then the resource definition and the parameter behavior. The mid-sentence enumeration of report sections is dense but each item earns its place by telling the agent what it will get back. Slightly list-heavy but no 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?

An output schema exists, so return-value structure needn't be explained; the description instead frames what the report covers, which is the right split. Combined with the preview caveat and the id-optionality rule, an agent has enough to call it correctly. Only report lifecycle details (retention, availability window) are absent.

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% and the single parameter is already fully documented in the schema, including the "omit for the latest import" behavior. The description restates that same guidance almost verbatim rather than adding format or edge-case detail. Baseline 3 is appropriate when the schema carries the semantics.

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?

Names a specific resource (the stored import report) and enumerates its contents: what was imported, skipped and failed, DNS changes per domain, outstanding work, and the code change. Adds source-provider scope (SendGrid, Postmark, Mailgun, Resend, Amazon SES), which no sibling covers. An agent can tell this apart from get_deliverability or get_dmarc_report immediately.

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?

"Pass the import id, or omit it for the latest import" gives an explicit call pattern, and "Previews are not stored" is a genuine exclusion that tells the agent not to expect a report after a preview run. No named alternative tool is offered, but there is no obvious competing retrieval path in the sibling list.

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