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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so 'never sends' largely restates them rather than adding new behavioral information. With annotations carrying the safety profile, the description still fails to explain what the preview resolves against when contactId, campaignId, and sequenceId are all optional, or what the returned preview contains (though an output schema exists).

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 short, front-loaded sentences with no filler; the preview-never-sends constraint lands early. It is arguably too terse rather than too long, but nothing is wasted.

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 covers return values, but for a tool with 8 optional parameters and no required ones, the description leaves a major gap: an agent cannot tell which parameter combinations are valid or how the target message is selected. That guidance is necessary for correct invocation and is entirely 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 description coverage is 0% across 8 parameters, so the description must compensate and does not. 'A selected contact' weakly implies contactId, but nothing explains campaignId vs sequenceId, which are alternatives, what happens when several are supplied, or what the external* and idempotencyKey parameters mean.

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?

States a concrete verb+resource: resolves the email a selected contact would receive, with the explicit scope that it never sends. It is distinguishable from generate_campaign_copy and launch_campaign, though it never names the closest siblings preview_audience and preview_sequence to sharpen the boundary. The 'APP:' prefix is unexplained noise but doesn't obscure the purpose.

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?

'Preview only; never sends' implies a pre-send verification use case and rules out the launch path. However, it gives no guidance on when to use this versus preview_sequence or generate_campaign_copy, and no prerequisites (e.g., whether a campaignId or sequenceId must exist first).

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