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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the safety profile is covered without description help. The description adds real behavioural context beyond that: it discloses that customer-match lists are included in the result set and that IDs split into include vs exclude semantics. It says nothing about pagination or the effect of 'limit', which is the one behavioural trait an agent would trip on.

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 dense sentences with no padding; the resource definition and the include/exclude usage come first. It could be tightened, but nothing is filler and the front-loading is correct.

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?

This is a low-complexity read-only list tool with 2 parameters and an output schema, so return values need not be described. Purpose and the workspace parameter are covered; the only real hole is the unexplained 'limit' and absence of any pagination note.

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 description coverage is 0%, so the description must compensate. It does explain 'workspace' well (slug of the customer workspace, optional when only one workspace exists), which is meaning the schema does not carry. However, 'limit' (default 100) is completely unaddressed, leaving half the parameters undocumented.

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?

States the resource precisely — Custom Audiences of Meta ad accounts, explicitly including Customer-Match lists — and names the concrete output (IDs). It does not literally say 'list', but the verb is implied unambiguously by the name and by the ID-consumption framing. It is clearly distinguishable from meta_list_pages, meta_list_pixels and the sibling ads_list_audiences (different platform).

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 tells the agent what the returned IDs are FOR — passing them as custom_audience_ids or excluded_custom_audience_ids into meta_create_adset/meta_update_adset, with the existing-customer exclusion case spelled out. That is genuine downstream guidance, but there is no statement of when to call this tool rather than alternatives, nor any prerequisite or exclusion context.

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