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

No annotations are provided, so the description carries the full disclosure burden. It does describe the output shape, status filtering, and per-event timestamps. However, it does not mention pagination behavior beyond the schema's limit parameter, ordering, rate limits, or potential failure modes.

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 core operation and return shape, and the usage examples earn their place by clarifying when to call the tool. It is slightly longer than strictly necessary, but every sentence adds useful 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?

For a fairly simple list tool with three parameters and no output schema, the description covers the purpose, output fields, optional filtering, and practical use cases. Minor gaps remain around pagination and ordering, but an agent has enough to invoke the tool correctly.

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%, so the schema already documents all three parameters. The description adds meaning by giving concrete filter examples ('status='opened'' for everyone who opened), but it mostly restates what the schema already communicates.

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 states a specific verb and resource: list per-recipient status for one campaign, enumerates the exact fields returned, and covers the event types. It distinguishes itself from sibling tools like campaigns_analytics by focusing on per-recipient rows rather than aggregate analytics.

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?

The description provides clear use cases ('who didn't open my newsletter', 'who clicked the call-to-action') and shows how the status filter supports them. It does not explicitly name sibling alternatives or explain when not to use the tool, but the practical examples give strong contextual guidance.

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