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

Annotations already declare readOnlyHint=true and destructiveHint=false, so the safety profile is covered. The description adds value by specifying return metrics and date/breakdown support, but it does not disclose potential edge behaviors such as default date ranges, pagination, or data availability delays. No contradictions with 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 three sentences with no filler. The first sentence front-loads the primary purpose, and the remaining sentences efficiently list return values and key options. It is appropriately sized for the tool's complexity.

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 6-parameter read-only tool with full schema coverage and no output schema, the description is serviceable but not fully complete. Missing details include the 'account' entity type, default date handling when dates are omitted, and guidance on how this tool compares to other ad-reporting siblings. The description plus schema is adequate for basic invocation but leaves decision-making gaps.

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 descriptions cover 100% of parameters, so the baseline is 3. The description adds a list of returned metrics and mentions date range/breakdown, but it mostly echoes schema information. It also says 'breakdown by day' while the schema supports week, month, and platform, which is slightly misleading but not harmful.

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 ('Get') and resource ('performance metrics for campaigns, ad sets, or creatives'), and lists the returned metrics. It is clear and generally distinguishes from post-level analytics, though it omits the 'account' entity type allowed by the schema and does not explicitly differentiate from get_unified_ad_report.

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 no explicit guidance on when to use this tool versus alternatives like get_unified_ad_report, get_post_analytics, or get_analytics. It only describes capabilities, leaving the agent to infer context from sibling tool names rather than giving direct selection criteria.

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