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 covered. The description adds behavioral context beyond annotations by listing the concrete metrics returned, supported aggregation levels, and a hook-comparison routing behavior. It does not contradict 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 front-loaded with the core purpose and immediately useful metric list. The second routing paragraph is dense but relevant to the tool's use in comparing hook-tagged campaigns. No fluff or repetition, though the routing note could be clearer for agents unfamiliar with draft_ad_variants conventions.

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 reporting tool with rich annotations and fully described parameters, the description covers the essential invocation context: what metrics come back, what levels are supported, and how to route hook comparisons. With no output schema, it partially compensates by enumerating returned metrics, though exact response field names are not specified.

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 input schema has 100% description coverage, with each parameter already documented (level, time_range, date_preset, campaign_id, ad_account_id, companyId). The description restates level and window concepts but adds little parameter-specific meaning beyond the schema. Baseline 3 is appropriate because the schema carries the explanatory weight.

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 opens with a specific verb and resource ('Get Meta ads results') and enumerates the exact metrics returned (spend, impressions, clicks, CTR, CPC, CPM, reach, conversions, cost per action, ROAS), levels, and window. It also explicitly names Facebook/Instagram, distinguishing it from siblings like get_x_ads_performance without needing to open schemas.

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 an explicit 'Use when the user asks how their Facebook/Instagram ads are doing' trigger, plus a routing rule for comparing hook-tagged campaigns. It does not explicitly name alternative tools or when-not-to-use cases, but the platform-specific trigger and sibling landscape make the intended context clear.

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