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

The annotations already declare this a safe, read-only, open-world operation, so the description does not need to re-litigate safety. It adds the scoping behavior (whole account by default, one campaign/ad set optionally), which is real context, but says nothing about volume of rows, ranking of results, or rate limits beyond what the detail parameter already documents in the schema.

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?

Two sentences, front-loaded with the core capability and followed by the scoping caveat. The long dimension list is necessary content, not padding, and there is no filler or hedging.

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 10 parameters, no output schema, and an open-world read, the description is complete on the input side (dimension list plus optional scoping) but silent on what an agent gets back, e.g. which metrics appear per row or how many rows a default summary contains. That is a notable gap for a reporting tool with no return-value schema.

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 description expands the opaque "platform" enum dimension by naming the four surfaces (Facebook/Instagram/Audience Network/Messenger), and enumerates the dimension choices in readable prose rather than raw enum tokens. It leaves date_range, detail, language, folder and account to the schema, which covers them adequately at 70% coverage, so this is meaningful added meaning rather than repetition.

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?

"Break performance down by age, gender, ... country, region, platform, placement, device or hour of day" gives a specific verb plus an exhaustive list of the resources being sliced, so an agent knows exactly what the call produces. It does not, however, distinguish itself from close siblings such as meta_insights_query, meta_performance, or meta_ads, which likely overlap heavily.

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?

"Optionally for one campaign or ad set" implies the default is account-wide and narrowing is opt-in, which is useful context. But there is no explicit when-to-use versus meta_insights_query/meta_performance, and no stated preconditions such as needing an enabled account or a folder.

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