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

Annotations already declare this as a safe, read-only, idempotent, non-destructive operation. The description adds useful behavioral context by listing the aggregate metrics returned and explaining the alternate per-recipient mode, though it does not mention auth requirements, rate limits, or pagination behavior.

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 primary purpose and followed by the key mode switch. Every sentence earns its place with no redundant or vague language.

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 read-only analytics tool with no output schema, the description sufficiently lists the returned metrics and explains the per-recipient mode. Minor gaps remain, such as not explicitly describing the `id` parameter or the `limit` behavior, but the core information needed to call the tool correctly is present.

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 75%, so most parameters are documented in the schema. The description adds meaning beyond the schema by clarifying that `recipients: true` changes the result shape to per-recipient rows and that `status` filters only in that mode, which the individual schema descriptions do not make explicit.

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 clearly states that this tool returns analytics for a single campaign and enumerates the metrics (sent, delivered, opens, clicks, bounces, etc.). It does not explicitly name or distinguish itself from the sibling `campaigns_manage` tool, but the read-only analytics scope is evident from the wording and title.

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 explains a key mode switch: setting `recipients: true` returns per-recipient rows instead of aggregate stats. However, it provides no explicit guidance on when to use this tool versus alternatives like `campaigns_manage`, nor any exclusions or prerequisites.

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