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

Annotations already declare readOnlyHint, destructiveHint, and idempotentHint. Description adds context that audiences are 'reusable' and 'owned by the API-key account,' which are behavioral traits beyond the annotations. No contradiction.

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?

Single sentence with clear verb-first structure. Every word is necessary; no filler. Highly concise and 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?

Given the tool has no parameters, known annotations, and an output schema (present but not detailed here), the description fully accounts for what's needed: it lists reusable audiences owned by the API-key account. Complete for its simplicity.

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?

No parameters in input schema (0 params, coverage 100%). Description adds meaning by specifying what is listed (reusable audiences, ownership). Baseline for 0 params is 4, and description meets it.

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?

Description uses specific verb 'List' and identifies the resource 'reusable marketing audiences' with ownership scoping 'owned by the API-key account.' Clearly distinguishes from sibling tools like get_marketing_audience and create_marketing_audience.

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?

Explicitly states what it does (list audiences) and the ownership scope. Though it doesn't mention when not to use, the simplicity of the operation makes context clear. No alternative tools are named, but the sibling list suggests uniqueness.

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