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

Annotations already declare readOnlyHint=true, idempotentHint=true, openWorldHint=true, and destructiveHint=false, so the safety profile is covered. The description adds useful behavioral context about what the report contains — benchmark comparisons, pattern identification, and prioritized recommendations — but does not clarify data scope (e.g., which campaigns or time range) or behavior when no campaign data exists.

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 efficiently enumerates the report's value. Every clause contributes to the agent's understanding of the output; there is 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 and no parameters, the description carries most of the burden for explaining what the tool returns, and it does describe the report contents well. It leaves minor gaps around data scope (all-time vs. recent campaigns) and whether prerequisites exist, such as needing prior campaign history.

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?

The tool takes zero parameters and has 100% schema coverage, so there is nothing to document. The description appropriately implies the report is generated from the account's existing data without requiring input parameters. Baseline 4 applies for a zero-parameter tool.

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?

States a specific verb and resource: 'Generate a comprehensive email marketing best practices report based on your actual campaign performance data.' The report contents are enumerated (benchmarks, patterns, improvement areas, recommendations). It does not differentiate itself from similar analytical siblings like campaign_health_dashboard or analyze_campaign, which keeps it from a 5.

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?

Usage is implied by 'based on your actual campaign performance data,' suggesting it is an account-level analysis. However, there is no explicit when-to-use guidance, no exclusions, and no mention of alternatives such as campaign_health_dashboard or analyze_campaign.

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