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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false, and openWorldHint=false, covering the safety profile. The description adds the downstream dependency on create_meta_adset, which is useful integration context but does not disclose pagination, rate limits, or other execution traits.

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 tightly written sentences: the first delivers the core purpose, the second adds the key downstream usage. No filler or redundancy, and the purpose is 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?

For a simple read-only list tool with an output schema and rich annotations, the description covers the essential purpose and the critical downstream integration. The main gap is the unexplained account_id parameter and lack of sibling differentiation, but the overall definition is serviceable given the structured metadata.

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 single required parameter account_id has 0% schema description coverage, and the description never explains what account_id represents or its expected format. Mentioning 'the Meta ad account' is the only hint, which is insufficient to compensate for the missing schema documentation.

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 states a specific verb ('Lists') and resource ('custom audiences') and scopes the resource with parenthetical types. It does not explicitly name or differentiate from sibling tools like list_meta_saved_audiences, so it stops short of the 5-level sibling routing detail.

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 implies when to use by noting the returned audience_id values feed into create_meta_adset, but it never states explicit when-to-use conditions or alternatives to this tool. No exclusions or comparisons to other list_* audience tools are provided.

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