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

Annotations already declare read-only/idempotent/non-destructive, and the description adds the auth requirement and the 'credentials_required until set' behavior, which goes beyond the annotations. It doesn't mention pagination, but for a read-only retrieval tool this is sufficient extra context.

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: the first describes the resource and output, the second covers the query options and auth requirement. Every clause carries distinct, useful information with no filler, and the key details are front-loaded.

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, the description provides a list of output fields (id, pageName, etc.), which is valuable. It also notes the gate/auth failure mode. It leaves limit clamping and country default to the schema, which is acceptable since the schema documents them, and the overall picture is complete enough for an agent to anticipate behavior.

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 coverage is 100% with descriptive parameter comments, so baseline is 3. The description repeats the q OR pageId constraint already present in the schema, but adds no new format details or clarifications. It does not add meaningful value beyond what the schema already provides.

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 tool as retrieving Meta Ad Library records, specifying the exact output shape (Ad[] with fields). It is distinct from sibling tools by naming the platform (Facebook/Instagram) and the specific data source, so an agent knows exactly when to select it.

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 gives direct usage instructions ('Provide q OR pageId') and states a key prerequisite (operator-side face_ACCESS_TOKEN with ads_read). It doesn't explicitly mention alternatives, but the platform-specific scope strongly implies when this tool is appropriate relative to the social_search siblings.

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