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

Annotations already declare readOnly, idempotent, and non-destructive, so safety is covered. The description adds the thing annotations cannot: an explicit auth prerequisite with two concrete paths (host OAuth prompt, or a Bearer acd_live_… API key header) and the URL where the key is created — genuinely actionable context that prevents a failed first call. It does not add rate-limit or pagination context, keeping it below a 5.

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 sentences, with purpose and payoff front-loaded and the auth block clearly demarcated by a capitalized label. Every clause carries information — there is no filler or repetition of the title.

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 the description is not obliged to describe return values, and the annotations cover the safety profile. What would otherwise cause a call to fail — authentication — is spelled out with both credential paths and a signup URL. Nothing an agent needs in order to invoke this correctly is missing.

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 tool takes zero parameters, which is the baseline-4 case; there are no argument semantics to explain. The field list in the description is a preview of results rather than parameters, so it neither helps nor hurts here.

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 ('List') plus resource ('the account's saved brand profiles'), with the returned fields enumerated (name, site, value props, CTA, tone, product images). It is clearly distinguished from the mutating sibling import_brand_profile, and the closing clause states the business reason the list exists.

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 clause 'so ads for the same brand reuse the same facts' tells the agent this is the read step that precedes ad generation for an existing brand, which is real usage context. It never names import_brand_profile as the alternative for creating a profile, nor states an exclusion, so it stops short of full when/when-not guidance.

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