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

Goes well beyond the annotations: it discloses the additive-only semantics, that retries are safe (corroborating idempotentHint), that access and plan eligibility are validated first, and a genuine side effect — with link sharing on, the Audiences and their Minds become publicly readable. That privacy consequence is not derivable from destructiveHint=false or openWorldHint=true.

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 tightly packed sentences with the core action front-loaded, followed by return values, retry safety, side effect, and preconditions — no filler or redundancy despite the density.

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-shape explanation is not required, and the description still names the attached/alreadyAttached result fields. Combined with annotations and 100% schema coverage, it supplies everything needed to invoke the tool correctly, including the public-visibility caveat.

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 100% and both parameters are documented in detail (uuid patterns, 1–50 item bound, study id/name precedence, active-Study fallback). The description only restates the 'existing, accessible' qualifier for audienceIds, so the baseline 3 applies.

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?

Specific verb+resource ('Adds existing accessible Audiences' to a Study) with an explicit scope qualifier — it does not remove others, plan, or start research — which separates it from delete/update/start_study_run siblings. An agent can identify the operation without opening the 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?

'Adds existing accessible Audiences' plus 'Access and plan eligibility are validated first' constrains when the call applies and implies the audiences must already exist (routing away from create_audience_from_brief / import_audience_sources). No sibling is named explicitly as the alternative, so it stops short of a full when/when-not statement.

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