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

The description discloses that PII is SHA-256 hashed and normalized automatically, and mentions bulk support via audience_ids. It also clarifies that destructive actions are in a separate tool, aligning with destructiveHint=false. These details add meaningful behavioral context beyond 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 verbose and includes both create and add_users actions before clarifying it is flattened to create. The structure could be more concise and front-loaded with the specific action. The bulk support statement adds a separate concern, making the text somewhat unfocused.

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?

Given no output schema, the description should explain return values or success indicators, but it does not. It lacks details on required parameters (though none are marked required), authentication prerequisites, and error handling. It covers user data normalization and bulk support but remains incomplete for a transactional create operation.

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 0%, so the description must compensate. It explains the users format (array of {email, phone?, fn?, ln?}) and audience_ids for bulk execution, but it does not describe name, account, description, audience_id, or auth_account. With 7 parameters and no schema descriptions, this is insufficient coverage.

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 includes 'create a new custom audience' within the actions list, and the '[Flattened action: create]' clarifies the current tool's purpose. However, the opening line 'Manage Custom Audiences for targeting' is broader and also lists 'add_users', which belongs to a sibling tool, causing slight ambiguity about the specific resource.

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 explicitly points to meta_ads_audience_delete for destructive delete, providing an alternative for a related operation. But it does not clearly state when to use this tool over meta_ads_audience_write_add_users, nor does it describe scenarios for creating audiences. The guidance is implicit rather than explicit.

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