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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is clear. The description adds useful behavioral context by clarifying that sent_dry represents dry-run records where nothing was delivered and that rates identify their denominator. It does not cover authentication or rate limits, but it meaningfully supplements the annotations.

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 a single, front-loaded sentence that immediately states the aggregation dimensions and then enumerates the metrics. Every phrase contributes to defining the report contents, and the final clause about rates clarifies denominator semantics without excess. There is no repetition or wasted text.

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, the description carries the burden of explaining return values, and it does so by enumerating all count categories and mentioning rates. The breakdown dimensions (per campaign, per step, per variant) are stated. It stops short of detailing the exact response structure or nesting, but it is sufficiently complete for an agent to understand what the tool returns.

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?

There is only one parameter, campaign_id, and the schema description coverage is 100%, so the schema already carries the parameter burden. The description does not add any syntax, format, or constraint details beyond what the schema provides. A baseline score of 3 is appropriate when the schema fully documents parameters.

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 is a reporting tool returning campaign metrics broken down per campaign, step, and variant. It enumerates the specific counts and rates, which distinguishes it from simple retrieval tools like get_campaign. It does not explicitly name siblings, but the resource and output are specific enough for an agent to identify the tool's 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?

The description explains what the report contains but gives no guidance on when to use it versus alternatives such as get_campaign, list_campaigns, or simulate_campaign. There are no prerequisites, exclusions, or contextual triggers mentioned. The agent must infer that this is the analytics/reporting option from the metric list alone.

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