Create Custom Audience

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

Annotations only show readOnlyHint=false, openWorldHint=false, idempotentHint=false, and destructiveHint=false, so the description carries the burden of behavioral disclosure. It adds valuable context: the audience is created but not populated, and population requires a separate Audiences API step. It also states the return value, which is useful since there is no output 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?

The description is well-organized with a one-sentence purpose, a supported-types bullet list, an Args list, a Returns line, and a clarifying Note. Every section adds information an agent needs, and it remains readable despite its length.

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 create operation with no output schema, the description covers the return value, subtype specifics, and the important caveat that audience population is separate. It does not explain the WEBSITE and APP subtypes it lists in the Args section, and it lacks explicit routing guidance against sibling audience tools, leaving minor gaps.

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 substantial meaning beyond the schema: ad_account_id gets an example format ('act_123456789'), CUSTOM subtype gets the Pixel requirement, customer_file_source gets its enum values explained, and retention_days gets a 1–180 range and optional flag. It only omits response_format, but that parameter is self-explanatory and already documented 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 the verb and resource: 'Creates a new custom audience in a Meta ad account.' It lists supported types and returns the new audience ID. However, it does not explicitly distinguish this from sibling tools like meta_create_saved_audience or meta_create_lookalike_audience, though the 'custom audience' wording provides some differentiation.

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 implies usage through the supported types list (CUSTOM, ENGAGEMENT, VIDEO) and notes that population is a separate step, which helps scope the tool. It does not explicitly say when to use this tool versus alternatives, nor does it provide exclusions or direct references to sibling audience-creation tools.

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