EU spend and reach

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

Annotations already declare read-only, idempotent, and non-destructive, but the description adds meaningful extras: the META_ADS_ARCHIVE_TOKEN requirement and the critical non-error empty-result behavior for unpublished data. This goes beyond what annotations and schema provide.

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?

Three sentences with no filler: core function first, scope second, and the important empty-result and auth notes last. Every sentence carries necessary information.

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?

Output schema exists, annotations cover safety, and the description covers purpose, scope, an important edge-case behavior, and the required token. An agent has enough to select and invoke this tool correctly without hidden surprises.

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?

All four parameters are already fully described in the schema with meaning for limit, query, country, and page_ids. The tool description does not add significant parameter-level semantics beyond that, so the baseline 3 is appropriate.

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 clearly identifies the resource (Meta's official Ad Library API) and the data returned (spend, impressions, reach, demographic breakdown). It also states the scope (EU-delivered ads and political or issue ads anywhere), which distinguishes it from general ad lookup tools.

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?

It provides clear context for when to use it: EU ads and political/issue ads anywhere, and explicitly says an ordinary US commercial ad will return nothing rather than an error. It doesn't name a specific sibling alternative, but the exclusion is enough to prevent misuse.

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