Create Lookalike Audience

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

Annotations indicate a non-read-only, non-idempotent mutation. The description confirms it creates a new resource and returns its ID, adding the prerequisite that it relies on an existing custom audience or page. It does not detail error conditions or side effects beyond creation, which is acceptable given the 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 concise and well-structured, starting with the main purpose and then listing arguments in a clear, readable format. It avoids extraneous detail and includes a brief return statement, making it easy for an agent to parse.

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?

The description covers all required parameters and the return value, but it does not explicitly differentiate this tool from sibling audience tools or mention the optional response_format. It also assumes knowledge of prerequisites without elaboration, leaving some context gaps for an agent.

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 adds meaning to ratio (range and explanation), origin_audience_id (source), and country (examples), which are beneficial since the schema lacks descriptions for ad_account_id and name. However, it omits the optional response_format parameter, though that is covered in the schema.

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 states that the tool creates a lookalike audience based on an existing custom audience or page, which is a specific and distinct action. It differentiates from sibling audience tools by the term 'lookalike', though the mention of 'page' is not fully reflected in the parameter description for origin_audience_id.

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 meta_create_custom_audience or meta_create_saved_audience. It only describes what it does without specifying conditions, exclusions, or when to prefer it over other audience-creation tools.

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