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

Annotations already declare readOnly/idempotent/non-destructive, so the safety bar is low. The description adds two things not in structured data: results are unconfirmed candidates, and calls cost no Adrails credits. It does not mention result volume, pagination, or how query narrows results.

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, action first, with the interpretive caveat and the cost note following. No repetition of the title and no filler.

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?

With a read-only annotation set, no output schema, and schema-documented parameters, the description covers what an agent needs to call it correctly and interpret the results. The remaining gap is how the returned candidates should be piped into a launch or sizing step, which is only hinted at.

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 coverage is 75% and the schema itself enumerates and explains all 11 kind values, so the schema does the heavy lifting. The description only names four of the kinds (audience, interest, language, location), leaving catalog, product-set, saved-audience, lead-form, instant-experience and page-event unmentioned outside the schema, and says nothing about query or accountIds.

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?

A specific verb ("Look up") plus a concrete resource ("actual platform audience, interest, language or location IDs") tells an agent exactly what comes back. It stops short of naming the sibling it differs from (audience_estimate), so 4 rather than 5.

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?

"Returned candidates are not confirmed launch choices" is a genuine usage caveat that implies this is a lookup step feeding a later launch decision. However, no explicit when-to-use statement, no exclusions, and no pointer to the alternative (audience_estimate) for sizing an audience.

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