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

Annotations already declare readOnlyHint, non-destructive and openWorld, so the safety profile is covered. The description adds genuinely useful behavior: the concrete return fields, the set of filterable outcomes, and the cursor loop ('pass next_after from the previous reply as after') plus the underlying endpoint. It does not mention rate limits or empty-result behavior, keeping it below a 5.

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 return content is front-loaded in the first clause, followed by filters, pagination mechanics and the endpoint — a logical order with little waste. The literal HTTP path is borderline noise for an agent but is defensible as operational context.

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 and seven parameters, the description carries real weight and does supply returned fields, filter semantics and pagination. Gaps remain around total counts, empty audiences and error/expired-cursor handling, but nothing essential for a correct call 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 coverage is 86%, so the schema already documents after, limit, category and the date bounds; the baseline is 3. The description mostly restates the enum values and cursor usage already present in the schema descriptions, and says nothing about sort or how start_date/end_date interact, so it adds little beyond the structured fields.

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 resource (campaign audience) and the exact fields returned (name, number, sent/delivered/read times), which clearly separates it from analytics or campaign-listing siblings. It never uses an explicit verb like 'list', instead opening with 'Who a campaign was sent to', so it is one step short of the crispest possible statement.

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 explains the optional filters (outcome, date range) and the cursor-pagination workflow, which implies when the tool is useful. But it never routes the agent away from alternatives — there is no mention of when to prefer get_campaign_analytics or how this differs from list_campaigns, and no prerequisite/exclusion guidance.

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