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

The readOnlyHint annotation already establishes this as a safe read, so the description's job is lighter. It does add useful context by enumerating the aggregate counters (sent, opened, clicked, bounced, unsubscribed, complained) that the response contains, though it says nothing about freshness, scope, or required permissions.

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?

One front-loaded sentence plus the API mapping; every clause earns its place with no filler.

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 usefully enumerates the returned counts so the agent knows what a report contains. For a single-parameter read tool this is nearly complete, though it omits any note on scope or time window of the aggregates.

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 100% for the single campaign_id parameter and the description adds no format or sourcing detail beyond it. Baseline 3 applies when the schema already carries parameter meaning.

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 gives a specific verb+resource ('Get a campaign's aggregate performance report') and enumerates the metrics returned, which differentiates it from the sibling links report by the word 'aggregate'. It does not name the sibling tool explicitly, so an agent must infer the distinction from context.

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?

There is no statement of when to use this versus get_campaign, get_campaign_links_report, or list_campaigns. Usage is only implied by the tool name and the endpoint path.

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