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

Annotations already declare readOnlyHint=true, idempotentHint=true, openWorldHint=false and destructiveHint=false, so the safety profile is fully covered without description help. The description adds modest behavioral context — that the returned audience includes an approximate size — but says nothing about pagination, limits, or whether the list is scoped beyond account_id.

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?

Three short sentences, front-loaded with the core action, then the definition of the resource, then the sibling disambiguation. No filler or redundancy.

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?

An output schema exists, so return fields need not be enumerated, and the description's 'approximate size' note is a useful extra. Combined with full annotation coverage, an agent has enough to call this correctly; only the account_id format is left entirely to inference.

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?

There is a single required parameter (account_id) with 0% schema description coverage, and the description never mentions it or its expected format. The parameter is largely self-evident from its name, but the description does not 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?

States a specific verb+resource (lists the account's SAVED audiences) and immediately defines what a saved audience is: a reusable targeting preset of interests + geo + demographics saved in Ads Manager. It explicitly names the nearest sibling, list_meta_audiences, and states how the two differ (custom/retargeting vs. saved presets), so an agent can disambiguate without opening either schema.

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?

Names the alternative tool, explains the semantic difference that selects between them, and gives the downstream use case ('Reuse their targeting when building ad sets'). An agent knows both when to call this and when to call the other one instead.

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