Create an ad group under a campaign (created paused unless status is given)

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

Annotations only declare readOnlyHint=false and openWorldHint=true; the description adds real behavioral context the annotations do not: the entity is created paused unless status is supplied, and the call is a dry run unless confirm=true. That default-paused and preview-by-default behavior is exactly the kind of pre-call surprise worth disclosing. It stops short of covering idempotency behavior or permission requirements.

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 tightly packed sentences with the action and the write protocol front-loaded, and no filler. Minor cost: stacked parentheticals and a phrase lifted almost verbatim from the title make it slightly denser than it needs to be.

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?

For a write tool with a deeply nested body (Bid/Money/Budget/Targeting) and no output schema, the description covers creation semantics and the dry-run gate but says nothing about what comes back (e.g., the new ad group ID) or how to recover it. Adequate to avoid a wrong call on safety, thin on the result side.

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 67%, so the schema already documents confirm and idempotencyKey. The description adds meaning only for the status field ('created paused unless status is given'); it says nothing about campaignId, targeting, bid, or budget semantics, so it does not meaningfully beat the baseline.

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 and resource ('Create an ad group') plus the parent scope ('under a campaign') and the backing endpoint (POST /v1/ad-groups). This clearly separates it from adGroups_list and adGroups_update in the sibling set.

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?

It tells the agent the execution protocol (dry run by default, set confirm: true to actually write), which is genuine usage guidance for the call itself. However, it never says when to reach for this versus adGroups_update or campaigns_create, nor what prerequisites exist (campaign must exist, targeting required).

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